JP2000077790A - Nitride semiconductor laser device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nitride semiconductor laser device which is possessed of a low threshold voltage at oscillation of laser rays and a small calorific value and capable of continuously oscillating at a room temperature. SOLUTION: A nitride semiconductor laser device has a structure where an N-type nitride semiconductor layer 2, an active layer 3, and a P-type nitride semiconductor layer 4 are successively laminated on a substrate 1, and a P- electrode 6 is formed on the P-type nitride semiconductor layer 4 through the intermediary of a current constriction insulating film 5 of SiO2. Furthermore, the P-type nitride SEMICONDUCTOR layer 4, the active layer 3, and the N-type nitride semiconductor layer 2 are partially etched to make the N-type nitride semiconductor layer 2 exposed so as to form a strip resonator where light is emitted from the active layer 3. A first flat plane 9 and a sloping plane 8 are so formed as to be parallel with the resonant direction of laser rays emitted from the active layer 3. An N electrode 7 is formed on the first flat plane 9 and the sloping plane 8.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser device made of a nitride semiconductor, and more particularly, to a technique for forming an electrode in a nitride semiconductor laser device.

[0002]

2. Description of the Related Art The recording density of an optical disk increases as the spot size of a light beam focused on the optical disk decreases, and the spot size of the light beam is proportional to the square of the wavelength of light. Therefore, in order to increase the recording density of the optical disk, it is necessary to shorten the oscillation wavelength of the semiconductor laser device as the light source.

At present, CDs mainly have a wavelength of 780 nm.
A GaAlAs semiconductor laser device that emits light in an (infrared) region is used, and an InGaAlP semiconductor laser device that emits light in a wavelength region of 650 nm (red) is used for a DVD having a higher recording density than a CD. In order to further increase the recording density of DVDs and record high-quality images, a semiconductor laser device that emits light in a blue region having a short wavelength is required.

As a semiconductor laser material used for a semiconductor laser device capable of realizing such a semiconductor laser device, a nitride semiconductor (In _x Al _Y Ga _{1 -XYN} , recently developed) has been developed.
0 ≦ X, 0 ≦ Y, X + Y ≦ 1) are attracting attention.

[0005] Nitride semiconductor laser devices include sapphire,
It is formed by epitaxially growing a nitride semiconductor laser material on a substrate made of a different material such as SiC or ZnO. When a nitride semiconductor laser material is epitaxially grown on an insulating substrate such as sapphire or ZnO to form a laser device, a p-type electrode and an n-type electrode are respectively formed from the p-type nitride semiconductor layer and the n-type nitride semiconductor layer. Must be formed on the same side.

FIG. 17 is a perspective view showing a conventional nitride semiconductor laser device, and FIG. 18 is a cross-sectional view as viewed from the longitudinal direction of the laser resonator of FIG.

A conventional nitride semiconductor laser device is shown in FIG.
As shown in FIG. 18, an n-type nitride semiconductor layer 2, an active layer 3, and a p-type nitride semiconductor layer 4 are sequentially laminated on a substrate 1. A p-electrode 6 is formed on the upper surface of the p-type nitride semiconductor layer 4 via a current constriction insulating film 5 made of SiO ₂ or the like. Further, the p-type nitride semiconductor layer 4, the active layer 3, and a part of the n-type nitride semiconductor layer 2 are removed by etching so that the n-type nitride semiconductor layer 2 is exposed. A band-shaped laser resonator L that emits more light is formed. Then, an n-electrode 7 is formed on the exposed n-type nitride semiconductor layer 2. In this way, a nitride semiconductor laser element is formed in which either the cleavage plane of the nitride semiconductor orthogonal to the strip-shaped laser resonator L or the chemically anisotropically etched surface is used as the light emitting end face of the laser.

In order to form a semiconductor laser device, it is important to form an optical resonance surface for oscillating a laser on a semiconductor layer. The optical resonance surface needs to be a flat mirror surface in order to oscillate a laser, and a conventional semiconductor laser device made of a GaAs-based or InGaAlP-based compound semiconductor has a cleavage property due to crystal properties. Therefore, the surface cleaved using this cleavage is formed as the optical resonance surface of the semiconductor laser device.

On the other hand, nitride semiconductors are hexagonal, and do not have cleavage properties unlike conventional GaAs-based ones. Furthermore, nitride semiconductors are often grown and formed on the surface of a sapphire substrate, and sapphire also has no cleavage due to its crystalline nature. Therefore, when a laser element is formed from a nitride semiconductor, it is difficult to make the cleavage plane an optical resonance plane as in a GaAs-based laser element.

Therefore, a technique for solving such a problem and forming an optical resonance surface on a nitride semiconductor having no cleavage is known.
It has been proposed in Japanese Patent Application Laid-Open No. H8-153931.

Japanese Patent Application Laid-Open No. 8-153931 has been proposed based on the finding that an optical resonance surface can be formed in a nitride semiconductor layer by dividing a sapphire substrate by a specific plane orientation. This shows that an optical resonance surface similar to the cleavage plane can be obtained from the nitride semiconductor layer stacked on the sapphire substrate having no cleavage and laser oscillation can be performed.

[0012]

As shown in FIGS. 17 and 18, an n-type and a p-type nitride semiconductor layers are formed on a substrate, and an n-electrode and a p-electrode are taken out from the respective layers. In the laser device, electrons from the n-electrode wrap around the exposed n-type nitride semiconductor layer and reach the active layer as shown by an arrow E, so that the flow of electrons does not go smoothly and the n-type nitride Since the voltage drop due to the semiconductor layer is large, the oscillation threshold voltage increases. In other words, since the threshold voltage is high, the amount of heat generated by the element itself increases, which causes a problem that the life of the element is extremely reduced and continuous oscillation becomes difficult.

Japanese Patent Application Laid-Open No. 10-75008 discloses that an n-electrode is formed on almost the entire surface of an n-type nitride semiconductor layer to reduce the voltage drop from the n-electrode to the active layer.
A device with a reduced threshold voltage is disclosed. Japanese Patent Application Laid-Open No. Hei 10-65213 discloses that an unevenness is provided at the interface between an n-electrode and an n-type contact layer, and the resistance value during energization is reduced between the p- and n-electrodes. Are disclosed.

However, even in these devices, the path from the n-electrode to the active layer via the n-type nitride semiconductor layer is not changed, and the electrons from the n-electrode are exposed to the exposed n-type. The semiconductor goes around the nitride semiconductor layer and reaches the active layer. Therefore, since the voltage drop due to the n-type nitride semiconductor layer is large, the oscillation threshold voltage is increased, the amount of heat generated by the element itself is increased, and there is a problem that the element life is extremely reduced and continuous oscillation becomes difficult. It has not been resolved.

On the other hand, as described in JP-A-8-153931, etc., in a nitride semiconductor laser device manufactured by a method of forming an optical resonance surface of a nitride semiconductor layer by cleavage, Due to the impact, the p-electrode formed on the optical resonance surface, which is the cleavage plane, easily floats or peels off, and there is a problem that a highly reliable nitride semiconductor laser device cannot be obtained.

Japanese Patent Application Laid-Open No. 10-27939 discloses that the end face of the p-electrode on the cleavage plane side is located inside the cleavage plane, so that the impact due to the break at the time of cleavage is not transmitted to the electrode end face, so that the electrode peels off. Are disclosed. However, if the p-electrode is made smaller so that the end face of the p-electrode is located inside the cleavage plane, the p-electrode and p
Since the contact area with the type nitride semiconductor layer is reduced, there remains a problem that the threshold value is increased or becomes unstable.

Further, in a nitride semiconductor laser device manufactured by a method of forming an optical resonance surface of a nitride semiconductor layer by cleavage, an impact at the time of cleavage or a scar at the time of scribing causes a damage on the n-type nitride semiconductor layer. The formed n-electrode is likely to float or peel off. If the n-electrode floats or peels off, conduction between the n-electrode and the n-type nitride semiconductor layer is not normally performed, the voltage drop increases, the oscillation threshold voltage increases, and the same problem as described above occurs.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a highly reliable nitride semiconductor laser device capable of lowering the threshold voltage at the time of laser oscillation and generating less heat and capable of continuous oscillation at room temperature.

[0019]

SUMMARY OF THE INVENTION In order to solve this problem, the present invention provides a method for reducing the electric resistance between p and n electrodes via an active layer on a substrate. An n-type nitride semiconductor layer, an active layer, and a p-type nitride semiconductor layer are sequentially stacked, and a part of the stack is removed and exposed so that the n-type nitride semiconductor layer in the stack is exposed. Semiconductor laser device in which a band-shaped laser resonator including a formed active layer is formed, an n-electrode is disposed on the exposed upper surface of the n-type nitride semiconductor layer, and a p-electrode is disposed on the upper surface of the p-type nitride semiconductor layer Wherein a part of the surface of the n-electrode on the side of the laser resonator side is brought into contact with the n-type nitride semiconductor layer.

As a result, the current is most concentrated on the contact surface on the side of the laser resonator side of the n-electrode whose distance from the active layer is shorter than the upper surface of the n-type nitride semiconductor layer. Can be reduced. Further, the area of the contact surface is increased, and similarly, the electric resistance value between the n-electrode and the active layer can be reduced. That is, the threshold voltage at the time of laser oscillation is lowered, so that a highly reliable nitride semiconductor device that generates less heat and can continuously oscillate at room temperature can be obtained.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention described in claim 1 of the present application is
An n-type nitride semiconductor layer, an active layer, and a p-type nitride semiconductor layer are sequentially stacked on a substrate, and a part of the stack is removed so that the n-type nitride semiconductor layer in the stack is exposed. Forming a band-shaped laser resonator including an exposed active layer, an n-electrode disposed on the exposed upper surface of the n-type nitride semiconductor layer, and a p-electrode disposed on the upper surface of the p-type nitride semiconductor layer A laser device, wherein a part of the surface of the n-electrode on the side of the laser resonator is in contact with the n-type nitride semiconductor layer, and the distance from the active layer is Is most concentrated on the contact surface of the n-electrode closer to the side of the laser resonator than the upper surface of the n-type nitride semiconductor layer, and the area of this contact surface is large. The electric resistance between the layers can be reduced.

According to a second aspect of the present invention, the contact surface of the n-electrode on the side of the laser resonator is provided such that the contact surface extends from the upper surface of the n-type nitride semiconductor layer to the side of the laser resonator. 2. The nitride semiconductor laser device according to claim 1, wherein a current is most concentrated on a slope which is a contact surface closer to an active layer than an upper surface of the n-type nitride semiconductor layer. In addition, since the area of the contact surface increases, the electric resistance between the n-electrode and the active layer can be reduced.

According to a third aspect of the present invention, in the method according to the third aspect of the present invention, the contact surface of the n electrode on the side of the laser resonator is provided so as to extend from the upper surface of the n-type nitride semiconductor layer to the side of the laser resonator. 2. The nitride semiconductor laser device according to claim 1, wherein a current is most concentrated on a side surface of a step having a contact surface closer to an active layer than an upper surface of the n-type nitride semiconductor layer. And the area of the contact surface increases, so that the electric resistance between the n-electrode and the active layer can be reduced.

According to a fourth aspect of the present invention, the contact surface of the n-electrode on the side of the laser resonator is a portion on the side of the laser resonator that is not in contact with the active layer. Wherein the distance from the active layer is closest to the upper surface of the n-type nitride semiconductor layer so that the current is most concentrated on the side surface of the laser resonator. In addition, since the area of the contact surface increases, the electric resistance between the n-electrode and the active layer can be reduced.

According to a fifth aspect of the present invention, an n-type nitride semiconductor layer, an active layer and a p-type nitride semiconductor layer are sequentially laminated on a substrate, and the n-type nitride semiconductor layer in the laminate is exposed. Forming a band-shaped laser resonator including an exposed active layer by removing a part of the same stacked body to form an n-electrode on the upper surface of the exposed n-type nitride semiconductor layer; A nitride semiconductor laser device having a p-electrode disposed on an upper surface of a layer, wherein a laser resonance surface of the laser resonator is formed by cleavage of a substrate, and a width of the p-electrode is reduced on a cleavage surface side. The formed nitride semiconductor laser device,
The impact applied to the p-electrode at the time of cleavage is reduced, and floating and peeling are less likely to occur.

According to a sixth aspect of the present invention, there is provided the nitride semiconductor laser device according to the fifth aspect, wherein the end face of the n-electrode on the cleavage plane side is formed inside the cleavage plane. The impact applied to the n-electrode at the time of cleavage or cleavage is reduced, and floating or peeling is less likely to occur.

According to a seventh aspect of the present invention, a notch for forming a split groove in which a part or the entirety of the n-type nitride semiconductor layer is removed between the end face of the n-electrode on the cleavage plane side and the cleavage plane. The nitride semiconductor laser device according to claim 5 or 6, wherein the n-electrode is not affected by an impact at the time of cleavage, so that the n-electrode does not float or peel off.

The invention according to claim 8 is the nitride semiconductor laser device according to any one of claims 5 to 7, wherein the n-electrode is the n-electrode according to any one of claims 1 to 4,
The current is most concentrated on the contact surface on the side of the laser resonator side of the n-electrode whose distance from the active layer is shorter than the upper surface of the n-type nitride semiconductor layer, and the area of this contact surface is increased. , The electric resistance between the n-electrode and the active layer can be reduced. Further, the impact applied to the electrode at the time of cleavage is reduced, and floating and peeling are less likely to occur.

(Embodiment 1) FIG. 1 is a perspective view showing a nitride semiconductor laser device according to a first embodiment of the present invention, and FIG. 2 is a cross-sectional view as viewed from the longitudinal direction of the laser resonator of FIG.

As shown in the drawing, the nitride semiconductor laser device according to the first embodiment of the present invention comprises an n-type nitride semiconductor layer 2, an active layer 3, and a p-type nitride semiconductor layer 4 on a substrate 1. Are sequentially laminated. A p-electrode 6 is formed on the upper surface of the p-type nitride semiconductor layer 4 via a current constriction insulating film 5 made of SiO ₂ . Further, the p-type nitride semiconductor layer 4, the active layer 3, and a part of the n-type nitride semiconductor layer 2 are etched to expose the n-type nitride semiconductor layer 2, and a band-shaped laser resonance emitting light from the active layer 3 is formed. A vessel L is formed.

At this time, the exposed n-type nitride semiconductor layer 2
A first plane 9 substantially parallel to the surface of the substrate 1 and a slope 8 provided from the first plane 9 to the side face 13 of the laser resonator have a resonance direction of laser light emitted from the active layer 3. And are formed in parallel. Here, "substantially parallel to the substrate surface" means that the surface roughness of the surface of the substrate 1 is within ± 10 ° with respect to a reference line. The angle formed by the slope 8 with the first plane 9 is 100 to 170 °. Then, an n-electrode 7 is formed on the first plane 9 and the slope 8 to obtain a basic structure of the nitride semiconductor laser device.

As described above, by bringing the slope 8 on the side of the laser resonator side surface 13 of the n-electrode 7 closer to the active layer 3 than the first plane 9 into contact with the end face 10 of the n-electrode 7, this contact is made. The current is most concentrated on the surface. At this time, the flow of electrons from the n-electrode 7 to the active layer 3 is as shown by the arrow E in FIG. 2, and the electric resistance between the n-electrode 7 and the active layer 3 can be reduced. Further, since the area of the contact surface is increased, the electric resistance value between n electrode 7 and active layer 3 can be reduced. Therefore, a highly reliable nitride semiconductor device capable of continuous oscillation at room temperature with a small amount of heat generation by lowering the threshold voltage during laser oscillation can be obtained.

(Embodiment 2) FIG. 3 is a perspective view showing a nitride semiconductor laser device according to a second embodiment of the present invention, and FIG. 4 is a cross-sectional view as viewed from the longitudinal direction of the laser resonator of FIG.

The nitride semiconductor laser device according to the second embodiment of the present invention is formed by a procedure similar to that of the first embodiment. However, the second plane 11, which is substantially parallel to the surface of the substrate 1 and corresponds to the upper surface of the step provided so as to extend from the first plane 9 to the side face 13 of the laser resonator, is parallel to the resonance direction of the laser light emitted from the active layer 3. It is formed so that The angle formed by the third plane 12 corresponding to the side surface of the step with the first plane 9 is set to 100 to 170 °. Then, the n-electrode 7 is placed on the first plane 9, the second plane 11, and the third plane 12.
To form a basic structure of a nitride semiconductor laser device.

As described above, by setting the third plane 12 on the side of the laser resonator side surface 13 of the n-electrode 7 closer to the active layer 3 than the first plane 9 as the contact surface, the contact surface is most The current becomes concentrated. At this time, the n-electrode 7
4 flows into the active layer 3 as shown by the arrow E in FIG. 4, and the electric resistance between the n-electrode 7 and the active layer 3 can be reduced. Further, since the area of the contact surface is increased, the electric resistance value between n electrode 7 and active layer 3 can be reduced. Therefore, a highly reliable nitride semiconductor device capable of continuous oscillation at room temperature with a small amount of heat generation by lowering the threshold voltage during laser oscillation can be obtained.

(Embodiment 3) FIG. 5 is a perspective view showing a nitride semiconductor laser device according to a third embodiment of the present invention, and FIG. 6 is a cross-sectional view as viewed from the longitudinal direction of the laser resonator of FIG.

The nitride semiconductor laser device according to the third embodiment of the present invention is formed by a procedure similar to that of the first embodiment. However, the slope 8 in the first embodiment.
Is not provided. Then, the n-electrode 7 having a large thickness is formed on the first plane 9. The end face 10 of the n-electrode 7 is brought into contact with the laser resonator side face 13 so as not to contact the active layer 3.

As described above, by bringing the laser resonator side surface 13 on the side of the laser resonator side surface 13 of the n-electrode 7 closer to the active layer 3 than the first plane 9 into contact with the end surface 10 of the n-electrode 7 The current is most concentrated on this contact surface. At this time, the flow of electrons from the n-electrode 7 to the active layer 3 is as shown by the arrow E in FIG. 6, and the electric resistance between the n-electrode and the active layer 3 can be reduced. Therefore,
By lowering the threshold voltage at the time of laser oscillation, a highly reliable nitride semiconductor element which generates less heat and can continuously oscillate at room temperature can be obtained.

The thickness of the n-electrode 7 is an important parameter for reducing the electric resistance between the active layers 3. Although the electrical resistance decreases as the film thickness increases, the upper surface of the n-electrode 7
When the electrons reach the p-type nitride semiconductor 4, electrons are hardly injected into the n-type nitride semiconductor 2 and do not form a pn junction or flow to the p-type nitride semiconductor 4 to be short-circuited. Therefore, it is necessary that the n-electrode 7 does not contact the active layer 3.

(Embodiment 4) FIGS. 7 and 8 are cross-sectional views of a nitride semiconductor laser device according to a fourth embodiment of the present invention as viewed from the longitudinal direction of a laser resonator.

The structure shown in FIG. 7 is different from the structure shown in FIGS. 1 and 2 in that the end face 10 of the n-electrode 7 is brought into contact with the side face 13 of the laser resonator, as in the third embodiment. Things. Thereby, for the same reason as in the third embodiment, the electric resistance value between n electrode 7 and active layer 3 can be further reduced. 8 is the same as that shown in FIGS. 3 and 4 as described above.

In either case, the flow of electrons from the n-electrode 7 to the active layer 3 is as shown by the arrow E in FIG. 7 or FIG. 8, and the electric resistance between the n-electrode 7 and the active layer 3 is further reduced. Can be done. Therefore, a highly reliable nitride semiconductor device capable of continuous oscillation at room temperature with a small amount of heat generation by lowering the threshold voltage during laser oscillation can be obtained.

(Embodiment 5) FIG. 11 is a perspective view showing a nitride semiconductor laser device according to a fifth embodiment.
FIG. 2 is a cross-sectional view as viewed from the longitudinal direction of the laser resonator of FIG.

The nitride semiconductor laser device according to the fifth embodiment of the present invention is formed by a procedure similar to that of the first embodiment. However, the width of the p-electrode 6 is formed to be narrow on the optical resonance surface side. Then, the band-shaped laser resonator L
The cleavage plane of the nitride semiconductor, which is substantially perpendicular to the above, is defined as the laser light emitting end face.

In the case where the optical resonance surface is formed by the cleavage method, the floating or peeling generated on the p-electrode 6 above the active layer 3 due to the impact at the time of scribing or cleaving does not occur on the entire surface of the p-electrode 6. It occurs at places where the adhesive strength is weak or where the strength of the impact at the time of cleavage is partially biased. Therefore, if the width of the p-electrode 6 is formed to be narrower on the cleavage plane side, the impact of the p-electrode 6 at the time of cleavage is reduced, so that the p-electrode 6 can be prevented from floating or peeling, and the threshold value increases or becomes unstable Disappears. That is, the threshold voltage at the time of laser oscillation is lowered, so that a highly reliable nitride semiconductor device that generates less heat and can continuously oscillate at room temperature can be obtained.

(Embodiment 6) FIG. 13 is a perspective view showing a nitride semiconductor laser device according to a sixth embodiment of the present invention, and FIG. 14 is a cross-sectional view as viewed from the longitudinal direction of the laser resonator of FIG.

The nitride semiconductor laser device according to the sixth embodiment of the present invention is formed by a procedure similar to that of the fifth embodiment. However, the end face 14 on the cleavage plane side of the n-electrode 7
Is formed beforehand on the inside of the position to be the cleavage plane. Then, the cleavage plane of the nitride semiconductor, which is substantially perpendicular to the band-shaped laser resonator L, is used as the light emitting end face of the laser.

When forming an optical resonance surface by the cleavage method, if an electrode exists on a line to be cleaved as an optical resonance surface,
The electrode receives shocks at the time of scribing and cleavage, causing floating and peeling.However, if the electrode is formed in advance inside the position to be the cleavage plane, the electrode receives less shock, and the floating or peeling occurs. Is less likely to occur, and the threshold value does not increase or become unstable. That is, the threshold voltage at the time of laser oscillation is lowered, so that a highly reliable nitride semiconductor device that generates less heat and can continuously oscillate at room temperature can be obtained.

When the p-electrode 6 is formed inside the cleavage plane,
The threshold value rises or becomes unstable,
Since the n-electrode 7 has a relatively large area as compared with the p-electrode 6, even if it is formed inside the cleavage plane, the threshold value increases,
The effect of becoming unstable is small. Rather, a nitride semiconductor laser device having high reliability due to little floating or peeling of the electrode can be obtained.

(Embodiment 7) FIG. 15 is a perspective view showing a nitride semiconductor laser device according to a seventh embodiment of the present invention, and FIG. 16 is a cross-sectional view as viewed from the longitudinal direction of the laser resonator of FIG.

The nitride semiconductor laser device according to the seventh embodiment of the present invention is formed by a procedure similar to that of the sixth embodiment. However, the end face 14 on the cleavage plane side of the n-electrode 7
Is formed in advance from a position to be a cleavage plane, and then a notch 15 for forming a split groove from which a part or the entirety of the n-type nitride semiconductor layer 2 is removed is formed. Then, the cleavage plane of the nitride semiconductor, which is substantially perpendicular to the band-shaped laser resonator L, is used as the light emitting end face of the laser.

When forming an optical resonance surface by the cleavage method, if an electrode exists on a line to be cleaved as an optical resonance surface,
The electrode receives a shock at the time of scribing or cleaving, which causes lifting or peeling. However, the electrode is formed beforehand at a position to be a cleavage plane, and further, the cleavage plane and the n-electrode 7 are formed.
Between the end face 14 on the cleavage plane side of the n-type nitride semiconductor layer 2
If the cleavage is performed after forming the notch 15 for forming the split groove from which a part or the whole is removed, the n-electrode 7 may float or peel off since there is no influence of the shock at the time of cleavage. And the threshold value does not rise or become unstable. That is, the threshold voltage at the time of laser oscillation is lowered, so that a highly reliable nitride semiconductor device that generates less heat and can continuously oscillate at room temperature can be obtained.

When the p-electrode 6 is formed inside the cleavage plane,
The threshold value rises or becomes unstable,
Since the n-electrode 7 has a relatively large area as compared with the p-electrode 6, even if it is formed inside the cleavage plane, the threshold value increases,
The effect of becoming unstable is small. Rather, a highly reliable nitride semiconductor laser device can be obtained due to no floating or peeling of the electrode.

[0054]

Next, specific examples of the present invention will be described.

The present embodiment shows a nitride semiconductor laser device manufactured by a gallium nitride based semiconductor layer grown by using the metal organic chemical vapor deposition method.

(Embodiment 1) This embodiment will be described with reference to FIGS.

First, a substrate 1 made of sapphire or the like whose surface is mirror-finished and the surface of which is C-plane is placed on a substrate holder in a reaction tube, and then the surface temperature of the substrate 1 is raised to 1100 ° C.
By keeping the substrate 1 for 0 minute and heating the substrate 1 while flowing hydrogen gas, cleaning for removing organic dirt and moisture adhering to the surface of the substrate 1 is performed.

Next, the surface temperature of the substrate 1 is lowered to 600 ° C., nitrogen gas as a main carrier gas is 10 l / min, ammonia is 5 l / min, and trimethyl aluminum (hereinafter referred to as “TMA”) is added. The n-type nitride semiconductor layer 2 which is a buffer layer made of AlN is formed to a thickness of 25 nm while flowing a carrier gas for TMA containing 20 nm / min.
Grown to a thickness of After that, the supply of the TMA carrier gas was stopped and the temperature was raised to 1050 ° C.
As a main carrier gas, a new carrier gas for trimethylgallium (hereinafter referred to as “TMG”) was supplied at 4 cc / min while flowing nitrogen gas at 9 liter / min and hydrogen gas at 0.95 liter / min. 10 ppm of Si
While flowing H ₄ (monosilane) gas at 10 cc / min.
After growing for 0 minutes, a first n-type layer made of GaN doped with Si is grown to a thickness of 2 μm. At this time, the carrier concentration of the first n-type layer is 1 × 10 ¹⁸ cm ⁻³ .

After the growth of the first n-type layer, while the main carrier gas and the carrier gas for TMG continue to flow at the same flow rate, only the flow rate of the SiH ₄ gas is changed to 50 cc / min, and the flow is continued for 6 minutes. Then, a second n-type layer made of GaN doped with Si is grown to a thickness of 0.2 μm. At this time, the carrier concentration of the second n-type layer is 5 × 10 ¹⁸ cm
^-3 .

An n-type nitride semiconductor layer 2 is formed by the first n-type layer and the second n-type layer. After growing and forming the n-type nitride semiconductor layer 2, the carrier gas for TMG and the SiH ₄ gas are stopped, the surface temperature of the substrate 1 is lowered to 750 ° C., and nitrogen gas is newly added as a main carrier gas at 10 liter / min. T
The carrier gas for MG is 2 cc / min, and the carrier gas for trimethylindium (hereinafter referred to as “TMI”) is 2 cc / min.
The active layer 3 made of non-doped InGaN is grown to a thickness of 6 nm by growing at a flow rate of 00 cc / min for 30 seconds.

Further, after the formation of the active layer 3, the carrier gas for TMI and the carrier gas for TMG are stopped, the surface temperature of the substrate 1 is raised to 1050 ° C., and 9 liters of nitrogen gas is newly added as a main carrier gas. / Min, hydrogen gas at 0.
94 liter / min, 4 cc / carrier gas for TMG
And a carrier gas for TMA at 6 cc / min, and biscyclopentadienyl magnesium (hereinafter referred to as "C
the p ₂ Mg "and referred to) carrier gas for grown 4 minutes while flowing at 50cc / min, AlG doped with Mg
A first p-type layer made of aN is grown to a thickness of 0.1 μm.

Subsequently, only the carrier gas for TMA was stopped, and at 1050 ° C., 9 L / min of nitrogen gas, 0.90 L / min of hydrogen gas, and TMG carrier gas were newly added as main carrier gases. 4 cc / min, Cp ₂
While flowing a carrier gas for Mg at 100 cc / min.
Then, a second p-type layer made of Mg-doped GaN is grown to a thickness of 0.1 μm.

The p-type nitride semiconductor layer 4 is formed by the first p-type layer and the second p-type layer. After the growth of the p-type nitride semiconductor layer 4, the carrier gas for TMG, which is a source gas, and ammonia are stopped, and the wafer is cooled to room temperature while flowing nitrogen gas and hydrogen gas at the same flow rate. Take out.

For the laminated structure including the quantum well structure formed of the gallium nitride-based compound semiconductor formed as described above, an insulating film 5 for current confinement made of a SiO ₂ film is deposited on the surface thereof by a plasma CVD method. The conditions for forming the current confinement insulating film 5 are as follows: the substrate temperature is 350 ° C., oxygen gas is 4 cc / min, and tetraethylorthosilicate is 10
While flowing at 0 cc / min, a film is formed at an RF power of 250 W for 30 minutes to form an SiO ₂ film having a thickness of 1 μm.

Next, a laser structure is formed on the wafer thus formed, and a nitride semiconductor laser device is manufactured.

First, as a method of forming a nitride semiconductor layer in a desired pattern, first, the current constriction insulating film 5 at a portion to be removed is removed by a wet etchant such as buffered hydrofluoric acid to form a mask having a predetermined shape. I do. Then, the p-type nitride semiconductor layer 4, the active layer 3, and a part of the n-type nitride semiconductor layer 2 are removed by dry etching with chemical anisotropy, and a plane substantially parallel to the substrate is exposed. Further, a mask having a predetermined shape is formed again, and dry etching with chemical anisotropy is performed to form a first plane 9 substantially parallel to the slope 8 and the substrate.

Then, in order to confine and inject a current into the active layer 3, the current confinement insulating film 5 on the p-type nitride semiconductor layer 4 is removed in a strip shape. The removal of the insulating film 5 for current constriction
A mask having a predetermined stripe shape is formed, and this is performed by a wet etchant such as buffered hydrofluoric acid. On the surface of the p-type nitride semiconductor layer 4 exposed by the etching as described above, a p-electrode 6 having a laminated structure of Ni and Au is formed by an evaporation method.

Next, the n-electrode 7 is connected to the first plane 9 and the slope 8
Form on top. At this time, the thickness of the n-electrode 7 is 3000 to
5000 angstroms, the height from the first plane 9 to the intersection of the slope 8 and the laser resonator side 13 is 5000 to 70
The angle between the slope 8 and the first plane 9 is set to be 120 to 145 °. The n electrode 7 is made of Ti
And Au are formed by an evaporation method so as to have a laminated structure.

Thereafter, the back surface of the substrate 1 is polished to 50 μm
Until thin. After polishing, the wafer on which the nitride semiconductor laser structure is formed is divided into laser elements.

First, using a scribe device, a first split groove is formed in a direction perpendicular to the stripe direction of the band-shaped pattern formed on the p-type nitride semiconductor layer 4. The first split groove has a groove width of about 5 μm and a groove depth of about 1 μm. Along the first split groove, the wafer is pressed and split from the opposite side of the first split groove using a breaking device. The end face formed in this manner is used as an optical resonance surface of the laser device. The first split grooves are formed at a pitch of 600 μm in the parallel direction, and the resonator length of the laser element is set to 600 μm.

Next, in the direction parallel to the band-shaped pattern formed on the p-type nitride semiconductor layer 4, a second split groove is formed using a scribing device at a pitch of 400 μm so that the laser element can be divided into single elements. Form. Using the breaking device, the substrate is split along the split groove from the opposite side of the split groove to produce a nitride semiconductor laser device.

As a result, a nitride semiconductor laser device having a size of 600 μm × 400 μm is manufactured.

When this nitride semiconductor laser device was placed on a heat sink and energized at the temperature of liquid nitrogen and laser oscillation was attempted, the oscillation wavelength at a threshold current of 800 to 900 mA was obtained for 80% or more of the laser devices obtained from the wafer. 4
Laser oscillation of 30 nm was confirmed. Further, Vf could be reduced to 50% as compared with the conventional product.

(Embodiment 2) FIGS. 3 and 4 described in the second embodiment by the same procedure as in Embodiment 1.
Is manufactured.

At this time, the width of the second plane is 3 to 10 μm,
The height of the third plane is 5000 to 15000 angstroms, and the width of the n-electrode 7 on the second plane 11 is 1 to 7 μm.

When this nitride semiconductor laser device was placed on a heat sink and energized at the temperature of liquid nitrogen to perform laser oscillation, an oscillation wavelength of 80% or more of the laser device obtained from the wafer at a threshold current of 800 to 900 mA was obtained. 4
Laser oscillation of 30 nm was confirmed. Further, Vf could be reduced to 70% as compared with the conventional product.

(Embodiment 3) FIGS. 5 and 6 described in the third embodiment by the same procedure as in Embodiment 1.
Is manufactured.

At this time, the height of the end face 10 of the n-electrode 7 is 3
It is formed to have a thickness of 000 to 9000 angstroms.

When this nitride semiconductor laser device was placed on a heat sink and energized at the temperature of liquid nitrogen and laser oscillation was attempted, the oscillation wavelength at a threshold current of 800 to 900 mA was obtained for 70% or more of the laser devices obtained from the wafer. 4
Laser oscillation of 30 nm was confirmed. Further, Vf could be reduced to 50% as compared with the conventional product.

(Embodiment 4) FIG. 7 or FIG. 8 described in the fourth embodiment by the same procedure as in Embodiment 1.
Is manufactured.

When this nitride semiconductor laser device was placed on a heat sink and energized at the temperature of liquid nitrogen to perform laser oscillation, at least 90% of the laser devices obtained from the wafer had an oscillation wavelength at a threshold current of 600 to 700 mA. 4
Laser oscillation of 30 nm was confirmed.

(Embodiment 5) In the example described in Embodiment 2, the angle formed by the third plane 12 with the first plane 9 is 12
9 and 10 show examples where the angle is 0 to 160 °. FIG.
FIG. 9 shows a case where the end face 10 of the n-electrode is in contact with the side face 13 in the resonator length direction in FIG. 9, which is a more desirable configuration for the same reason as in the third embodiment.

When this nitride semiconductor laser device was mounted on a heat sink and energized at the temperature of liquid nitrogen to perform laser oscillation, Vf could be reduced to 50% as compared with the conventional product.

(Example 6) The nitride semiconductor laser device shown in FIGS. 11 and 12 described in the fifth embodiment is manufactured by the same procedure as in Example 1. However,
When the SiO ₂ film 6 on the p-type layer is removed in a strip shape and the p-electrode 6 having a laminated structure of Ni and Au is formed by vapor deposition on the surface of the p-type layer exposed by etching, optical resonance occurs. The p-electrode 6 is formed such that the width of the p-electrode 6 in the direction perpendicular to the surface becomes smaller on the optical resonance surface side. The width of the p-electrode 6 at the end face of the optical resonance surface is 5
μm.

Even when the optical resonance surface of the nitride semiconductor laser device was formed by the cleavage method, the floating of the p-electrode was hardly confirmed, and no peeling occurred.

When this nitride semiconductor laser device was set on a heat sink and energized at the temperature of liquid nitrogen to perform laser oscillation, an oscillation wavelength of 90% or more of the laser devices obtained from the wafer at a threshold current of 900 to 1000 mA was obtained. 430 nm laser oscillation was confirmed.

(Example 7) By the same procedure as in Example 1, the nitride semiconductor laser device shown in FIGS. 13 and 14 described in the fifth embodiment is manufactured. However,
The n-electrode 7 is formed so as to be inside 20 μm from the optical resonance surface.

Even when the optical resonance surface of this nitride semiconductor laser device was formed by the cleavage method, the n-electrode was hardly lifted, and there was no separation.

When this nitride semiconductor laser device was placed on a heat sink and energized at the temperature of liquid nitrogen and laser oscillation was attempted, the oscillation wavelength was obtained at a threshold current of 850 to 950 mA for 85% or more of the laser devices obtained from the wafer. 4
Laser oscillation of 30 nm was confirmed.

(Example 8) By the same procedure as in Example 1, the nitride semiconductor laser device shown in FIGS. 15 and 16 described in the sixth embodiment is manufactured. However,
The notch for forming the groove provided in the n-type nitride semiconductor layer 2 is formed to have a depth of 1.5 to 2.0 μm.

Even if the optical resonance surface of this nitride semiconductor laser device is formed by the cleavage method, no floating of the n-electrode is confirmed at all.
There was no peeling.

When this nitride semiconductor laser device was placed on a heat sink and energized at the temperature of liquid nitrogen to perform laser oscillation, an oscillation wavelength of 80% or more of the laser devices obtained from the wafer at a threshold current of 850 to 950 mA was obtained. 4
Laser oscillation of 30 nm was confirmed.

[0093]

As described above, an n-type nitride semiconductor layer, an active layer and a p-type nitride semiconductor layer are sequentially laminated on a substrate, and the n-type nitride semiconductor layer in the laminate is exposed. A strip-shaped laser resonator including an exposed active layer is formed by removing a part of the same laminated body as described above, and an n-electrode is arranged on the upper surface of the exposed n-type nitride semiconductor layer. P on the top of
A nitride semiconductor laser device having an electrode disposed therein, wherein a part of a surface of the n-electrode on the side of the laser resonator side is brought into contact with the n-type nitride semiconductor layer, whereby an n-electrode and an active layer An electrical resistance value can be reduced, a threshold voltage at the time of laser oscillation can be reduced, and a highly reliable nitride semiconductor laser device that can generate continuous heat at room temperature with a small amount of heat generation can be realized.

Note that the contact surface of the n-electrode on the side of the laser resonator is on a slope provided from the upper surface of the n-type nitride semiconductor layer to the side of the laser resonator. , The electrical resistance between the n-electrode and the active layer can be reduced, and a nitride semiconductor laser device with a further reduced threshold voltage can be realized.

Also, the contact surface of the n-electrode on the side of the laser cavity is on the side of a step provided from the upper surface of the n-type nitride semiconductor layer to the side of the laser cavity. Thus, the electrical resistance between the n-electrode and the active layer can be reduced, and the threshold voltage can be further reduced, thereby realizing a nitride semiconductor laser device.

Further, the contact surface on the side of the laser resonator side of the n-electrode is located on a portion of the side surface of the laser resonator that is not in contact with the active layer.
The electrical resistance between the end face of the electrode on the resonator side and the active layer can be reduced, and a nitride semiconductor laser device with a further reduced threshold voltage can be realized.

An n-type nitride semiconductor layer, an active layer and a p-type
And a layer-shaped laser resonator including an exposed active layer is formed by removing a part of the stacked body so that the n-type nitride semiconductor layer in the stacked body is exposed. And
Disposing an n-electrode on the upper surface of the exposed n-type nitride semiconductor layer;
By arranging the p-electrode on the upper surface of the p-type nitride semiconductor layer, a high-reliability nitride semiconductor laser device that does not float or peel due to the impact at the time of cleavage, does not increase the threshold voltage, and does not become unstable. realizable.

Further, by forming the n-electrode end face on the cleavage plane side to be inside the cleavage plane, the threshold voltage rises or becomes unstable without floating or separation due to the impact at the time of cleavage. A highly reliable nitride semiconductor laser device can be realized.

Further, a notch for forming a split groove from which a part or the whole of the n-type nitride semiconductor layer is removed is formed between the end face of the n-electrode on the cleavage plane side and the cleavage plane.
Since the n-electrode will not receive any impact during cleavage,
The n-electrode does not float or peel off, and the threshold voltage does not increase or become unstable, so that a highly reliable nitride semiconductor laser device can be realized.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a nitride semiconductor laser device according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view as viewed from a longitudinal direction of the laser resonator of FIG. 1;

FIG. 3 is a perspective view showing a nitride semiconductor laser device according to a second embodiment of the present invention.

FIG. 4 is a cross-sectional view of the laser resonator of FIG. 3 as viewed from the longitudinal direction.

FIG. 5 is a perspective view showing a nitride semiconductor laser device according to a third embodiment of the present invention.

FIG. 6 is a cross-sectional view as viewed from the longitudinal direction of the laser resonator of FIG. 5;

FIG. 7 is a cross-sectional view of a nitride semiconductor laser device according to a fourth embodiment of the present invention, viewed from the longitudinal direction of a laser resonator.

FIG. 8 is a cross-sectional view of a nitride semiconductor laser device according to a fourth embodiment of the present invention as viewed from a longitudinal direction of a laser resonator.

FIG. 9 is a cross-sectional view of a nitride semiconductor laser device according to a fifth embodiment of the present invention, viewed from the longitudinal direction of the laser resonator.

FIG. 10 is a cross-sectional view of a nitride semiconductor laser device according to a fifth embodiment of the present invention, viewed from the longitudinal direction of the laser resonator.

FIG. 11 is a perspective view showing a nitride semiconductor laser device according to a fifth embodiment of the present invention.

FIG. 12 is a cross-sectional view as viewed from the longitudinal direction of the laser resonator of FIG. 11;

FIG. 13 is a perspective view showing a nitride semiconductor laser device according to a sixth embodiment of the present invention.

FIG. 14 is a cross-sectional view as viewed from the longitudinal direction of the laser resonator of FIG. 13;

FIG. 15 is a perspective view showing a nitride semiconductor laser device according to a seventh embodiment of the present invention.

FIG. 16 is a cross-sectional view of the laser resonator of FIG. 15 viewed from the longitudinal direction.

FIG. 17 is a perspective view showing a conventional nitride semiconductor laser device.

FIG. 18 is a cross-sectional view of the laser resonator of FIG. 17 viewed from the longitudinal direction.

[Explanation of symbols]

 Reference Signs List 1 substrate 2 n-type nitride semiconductor layer 3 active layer 4 p-type nitride semiconductor layer 5 current confinement insulating film 6 p-electrode 7 n-electrode 8 slope 9 first plane 10 end face 11 second plane 12 third plane 13 laser resonance Side 14 End face 15 Notch for split groove formation

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Shinichiro Yano 1006 Kazuma Kadoma, Kadoma-shi, Osaka Matsushita Electric Industrial Co., Ltd. F-term (reference) 5F041 AA24 CA04 CA05 CA34 CA65 5F073 AA61 AA73 BA06 CA07 DA05 DA30 EA07 EA29

Claims (8)

[Claims] 1. An n-type nitride semiconductor layer, an active layer and a p-type
And a layer-shaped laser resonator including an exposed active layer is formed by removing a part of the stacked body so that the n-type nitride semiconductor layer in the stacked body is exposed. And
Disposing an n-electrode on the upper surface of the exposed n-type nitride semiconductor layer;
A nitride semiconductor laser device in which a p-electrode is arranged on an upper surface of the p-type nitride semiconductor layer, wherein a part of a surface of the n-electrode on the side of the laser resonator is in contact with the n-type nitride semiconductor layer. A nitride semiconductor laser device characterized in that: 2. The method according to claim 1, wherein the contact surface of the n-electrode on the side of the laser resonator is on a slope provided from the upper surface of the n-type nitride semiconductor layer to the side of the laser resonator. The nitride semiconductor laser device according to claim 1, wherein 3. The method according to claim 1, wherein a contact surface of the n-electrode on the side of the laser resonator is on a side surface of a step provided from the upper surface of the n-type nitride semiconductor layer to the side of the laser resonator. 2. The nitride semiconductor laser device according to claim 1, wherein: 4. The laser device according to claim 1, wherein a contact surface of said n-electrode on a side of said laser resonator is located on a side of said laser resonator which is not in contact with said active layer. A nitride semiconductor laser device according to any one of the above. 5. An n-type nitride semiconductor layer, an active layer and a p-type
And a layer-shaped laser resonator including an exposed active layer is formed by removing a part of the stacked body so that the n-type nitride semiconductor layer in the stacked body is exposed. And
Disposing an n-electrode on the upper surface of the exposed n-type nitride semiconductor layer;
A nitride semiconductor laser device in which a p-electrode is arranged on an upper surface of a p-type nitride semiconductor layer, wherein a laser resonance surface of the laser resonator is formed by cleavage of a substrate, and a width of the p-electrode is set at a cleavage surface side. A nitride semiconductor laser device characterized by being formed so as to be narrower. 6. An n-electrode end face on a cleavage plane side is formed to be inside a cleavage plane.
22. The nitride semiconductor laser device according to claim 20. 7. A notch for forming a split groove from which a part or the entirety of the n-type nitride semiconductor layer is removed, between the end face of the n-electrode on the cleavage plane side and the cleavage plane. 7. The nitride semiconductor laser device according to claim 5, wherein 8. The nitride semiconductor laser device according to claim 5, wherein the n-electrode is the n-electrode according to any one of claims 1 to 4.