JPH0461184A - Surface luminescent semiconductor laser and manufacture thereof - Google Patents

Abstract

PURPOSE:To provide a low threshold current high light emission efficiency surface emitting semiconductor laser with the high yield by forming a semiconductor column as a light emitting region surrounded by a groove reaching a quantum well active layer, and further forming a modified layer on a semiconductor side surface of the groove. CONSTITUTION:There are crystal grown on an n-type GaAs semiconductor substrate 1 a first conductivity type semiconductor multilayered reflecting film 2 comprising 23 periods of n-type AlAs 802 Angstrom /n type GaAs 670 Angstrom , a quantum well structure active layer 3 comprising Al0.5 Ga0.5As 1430 Angstrom , a second conductivity type semiconductor multilayered reflection film 4, and a p<+> type GaAs 30 Angstrom capping layer 15. Further, a ring-shaped groove 7 issoformed by photoetching that it reaches the active later 3. Thereupon, a semiconductor column 6 is formed as a light emitting region. Then, an SiO2 film 5 as a mutual diffusion promoting film is formed over the entire surface of the substrate, and the SiO2 film 5 is etched using dry etching 12. Further, a modified layer (disordered region) 8 is formed only in the vicinity of the SiO2 film 5 on the side surface of the ring-shaped groove 7 by a heat treatment.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a surface emitting semiconductor laser used for optical exchange and optical information processing.

(Prior Art) In fields such as optical switching, optical computers, and optical information processing, surface-emitting lasers that can be two-dimensionally integrated are required, and are being actively researched and developed. An example is J.L.

Electronics Letters by Jewell, Y, H, Lee, etc.
s) Volume 25, pages 1123-1124 and 1377-13
78J4. It has been reported that a surface emitting laser with a diameter of 1 to 5 pm oscillated with a threshold current of 1 to 2 mA.

The manufacturing method was such that after forming a semiconductor layer, gold and Ni were vapor-deposited, Ni was patterned into a circle with a diameter of several micrometers, and semiconductor pillars with a diameter of several micrometers were formed by dry etching using Ni as a mask.

(Problem to be solved by the invention) In the surface emitting laser described above, the threshold current is about 1 mA,
The threshold current, which is subtracted from the threshold current density IK, A, /cm, has a diameter of 2□m, which is very large compared to 3O□A. The reason for this is that the active layer side on the meza side is popular (Russia: i3t,
, + '1. - structure, and furthermore, the damage caused when forming semiconductor pillars by dry J-tooling is reduced if
+i and through surface non-radiative recombination here /-1 reactive charge! Since L is about 1 mA, it is possible that the semiconductor pillar with a diameter of im has weak mechanical strength and may be damaged during the process, resulting in a decrease in yield, or the light emitting area G pass l -L, There is a problem that the luminous efficiency decreases due to heat/, -3, Off: For the same reason, it is difficult to fuse the heat sink to the growth surface side, so continuous wave However, the object of the present invention is to reduce the reactive charge* by surface recombination, thereby creating a surface-emitting semiconductor laser with low threshold current and high luminous efficiency. and its high-yield production].

(Means for Solving the Problems) The surface emitting semiconductor laser of the present invention has a semiconductor multilayer reflective film of a first conductivity type on a conductive substrate 7, and a quantum well structure having at least one quantum well structure. It has a semiconductor column that is a light emitting region and is surrounded by a groove that reaches the quantum well active layer, and includes at least a well RB layer and a semiconductor multilayer reflective film of a second conductivity type, and a metamorphic layer on the semiconductor side surface of the groove. It is characterized by having the following.

Alternatively, the present invention is characterized in that it is a planar surface-emitting laser or laser array in which the grooves of the surface-emitting laser of the present invention are filled with a resin such as boimide.

A surface emitting semiconductor laser manufacturing method of the present invention includes a semiconductor multilayer reflective film of a first conductivity type, a quantum well active layer having at least one quantum well structure, and a semiconductor multilayer reflective film of a second conductivity type, on a semiconductor substrate. a step of forming a semiconductor layer comprising at least a semiconductor layer; a step of forming a groove reaching the quantum well active layer by etching and forming a semiconductor column serving as a light emitting region surrounded by the groove; a step of forming an interdiffusion promoting film on the semiconductor surface; a step of removing the interdiffusion promoting film by directional dry etching except for the side surfaces of the groove; and the process of mutual diffusion.
It is characterized by being prepared.

Further, the second manufacturing method includes, on a semiconductor substrate, a semiconductor multilayer reflective film of a first conductivity type, a t-well active layer having at least one quantum well structure, and a semiconductor multilayer reflective film of a second conductivity type. a step of forming a semiconductor layer comprising at least a film; forming a groove reaching the FA active layer by etching, and forming a semiconductor column having a light emitting region surrounded by the groove]: 1r-1 A step of forming an interdiffusion promoting film including at least an insulating film on the semiconductor surface, a step of applying a nootresist to the interdiffusion promoting film 1- so that the groove becomes flat, and etching except for the trench. The method is characterized by comprising the steps of removing the interdiffusion promoting film, and performing interdiffusion in the groove by heat treatment to form a semiconductor metamorphic layer.

(Function) A heterojunction may be used to reduce the reactive current by surface non-radiative recombination, and as a means of achieving this, there is a technique of disordering by introducing impurities or the like.

This is done by introducing impurities into the active layer consisting of a quantum well structure.
＆：、、：SU、Thermal stress is applied to the composition of the quantum well structure. This disordered region is called a metamorphic layer1, which is referred to as a semiconductor with a wafer-like composition.
By making a semiconductor with a wider bandgap than the layer,
Surface recombination is suppressed by the hetero-LU junction effect. There were problems in applying this technology to surface emitting devices. In other words, the light emitting part of the surface emitting device is made of 8 semiconductors, etc., but if impurities or thermal stress are introduced into the entire surface to make it disordered, the area near the top 19 of the semiconductor The conductive multilayer film also becomes disordered and its reflectance decreases!
, T+), the resistance of the electrode increases [,5] and the laser characteristics deteriorate. The structure is formed only on the side m of the groove.

Furthermore, a groove is formed around the light emitting region σ door 1 knee conductor 1-
Unlike the conventional structure with a protruding light-emitting part, this structure maintains its mechanical strength and prevents damage during the manufacturing process and mounting process, reducing unnecessary stress on the light-emitting area. It has a structure that does not apply.

According to the manufacturing method of the present invention, the above-described cross-feeding can be easily manufactured with high yield. Manufacture No. 5 of Claim 2 of the present invention
In method 'Q, after forming semiconductor pillars by -]-soching, S
By removing an interdiffusion promoting film such as iO on the entire surface using a highly directional D-N-E etching method, such as anti-broadband etching (RIBE), S
Only the iO2 film is etched. Jri semiconductor 1+ to this
The SiO□ film on the side surfaces of ``1'' remains, and the SiO on flat areas such as the top of the conductor block ``1'' is removed. 1- After forming the amplification promoting film, heat treatment is performed, so there is no deterioration of the multilayer reflective film or electrodes.

6. The manufacturing knob method of claim 3, in which the metamorphic layer can be formed only on the side surfaces, forms the interdiffusion promoting film on the entire surface] up to two parts, as in claim 2. Then, apply photoresist and flatten the surface. The area of the grooves is smaller than the entire Gohar, so it can be easily applied evenly. Next, the photoresist is uniformly etched by dry etching or the like, but since the photoresist is thinner in the flat 1g portion of the semiconductor surface than in the groove portion, the photoresist is thinner. Next, the phase 7 color diffusion promoting film is removed from the flat portion by etching. In the groove portions, the photoresist is simply etched, but the interdiffusion promoting film is preserved. Thereafter, the photoresist is removed by cleaning and heat treatment is performed to introduce impurities or pores only into the grooves, forming a metamorphic layer. In this way, the quantum well active layer on the side surface of the semiconductor pillar can be disordered. Even with this method, there is no deterioration of the reflective film or electrode, and no accompanying increase in electrical resistance.

Furthermore, in the present invention, since the semiconductor pillar is formed by forming a groove around the periphery, the groove can be easily filled with polyimide to form a planar structure. In particular, by making the width of the surrounding groove constant, the shape of the polyimide embedded becomes constant and can be flattened with good reproducibility. After embedding, the polyimide on the top of the semiconductor pillar can be uniformly removed with good reproducibility by dry etching. In a laser array that integrates a large number of surface emitting lasers, in order to drive each one independently,
A lot of wiring has to be done. With conventional laser arrays, it is difficult to planarize them, and the height of the semiconductor pillars is about 2/, m, so wiring breaks easily occur and the yield is low.
Was. The present invention is easy to bus, and allows fine wiring even when the number of lasers increases, making it ideal for high-density integrated surface emitting laser arrays.

(Example) Next, an example of the present invention will be described in detail using the drawings. FIGS. 1(a) to 1(d) are cross-sectional views showing the manufacturing process of the σ-roux embodiment of the present invention. First, as shown in FIG. 1(a), on an n-type GaAs semiconductor substrate 1, a semiconductor multilayer reflective film 2 of the first conductivity type consisting of 23 periods of 802 n-type AIAs and 670 in-type GaAs, 143 A1o5Gao5As, is formed.
0 people/Ino2Gao8As10o included/A1o5Gao
Active layer 3 with quantum well structure consisting of 1430 5As, p
A semiconductor multilayer reflective film 4 of the second conductivity type with 10 cycles of 670 type GaAs and 802 types of AIA, and a cap layer 15 of 30 types of p-type GaAs are crystal-grown. Here, Ino. inside the active layer 3. 2Gao. The sAS layer is a positive single quantum well active layer.

Next, a ring-shaped groove 7 is formed using a normal photo-etching technique.
form. The etupung depth at this time is active layer structure 3
Make sure that it reaches. The etching method is a directional method such as reactive ion beam etching (RIBE method) or anti-J:II reactive ion etching method (RIE method) so that vertical side surfaces can be obtained. At this time, a semiconductor column 6 having a diameter of 2 to 5/m is formed as a light emitting region.

Next, the mutual diffusion promoting film 5i02 film (thickness 1,000~2
000 people) on the entire surface.

Next, the 5-layer film is etched using directional dry etching again. CF, etc. are used as niratin gas. As the etching method, the RIBE method or the RIE method may be used. At this time, since the etching beam 12 is directional, the etching speed of the SiO2 film 5 formed on the side surface of the ring-shaped groove 7 is extremely slow. Therefore, as shown in FIG. 1(b), the Si
Only the O.2 film 5 can be etched (Z). next,
Heat treatment is performed at 850° C. for about 1 hour to 10 hours in an As atmosphere. At this time, in order to prevent As from being desorbed from the GaAs surface, there is a method of protecting the surface with a GaAs substrate in an H2 atmosphere (face-to-face method), and a method of applying As powder and a Lely wool bar inside the quartz ampoule.゛It is recommended to follow a method such as creating an As atmosphere by cutting the ring-shaped groove 7. By this heat treatment, a metamorphic layer (disordered region) 8 can be formed only in the vicinity of the SiO2 film 5 on the surface of the ring-shaped groove 7. The reason why the crystal becomes dish-ordered near the 5i02 film 5 is due to the movement of A [atoms inside the crystal and t<3
102" AK5 is thought to be reduced, but the detailed mechanism is not clear. In addition to this method, the conventionally known method of Si diffusion may be used. In this case, SiN film/Si film 2 is used instead of SiO□ film 5.
Using a layered structure (again, as shown in FIG. 1(b), only the "T'" layer is used), and these layers are removed by etching.

Next, heat treatment is performed at 850°C for about 1 to 10 hours to cause 81 diffusion to occur in the SiN film on the side surface of the ring-shaped groove 7.
This occurs only in the vicinity of the Si film, and an n-type disordered region 8 is formed. In this case, the first conductivity type semiconductor multilayer reflective film 2
It is convenient to make the semiconductor substrate 1 a p-type and to make the second conductivity type semiconductor multilayer reflective film 4 an n-type because the pn junction is not exposed at the top of the semiconductor pillar. Also, instead of SiN film/Si film, Zn doped spin-on glass film, Zn do
A PE 5 pin on glass film (SOG film) can also be used. In this case, the disordered region becomes p-type.

Next, as shown in FIG. 1(e), polyimide 13 is applied to the entire surface so that it is even with the sweat. Next, dry etching using oxygen gas is performed until the top of the semiconductor pillar 6 is reached. At this time, by making the width of the ring-shaped groove 70 substantially constant, the thickness of the polyimide 13 on the top of the semiconductor pillar 6 can be made uniform within the wafer. Therefore, by dry etching polyimide, the top portions of the semiconductor pillars 6 can be exposed with a high yield. Next, Si
An N film 9 is formed, a window for forming an electrode is formed by ordinary photoetching, and a p-type electrode 10 is formed. In this case, since planarization is achieved using polyimide, no breakage occurs in the p-type electrode 10. Finally, n-type electrode 1
1 is formed, and a light output extraction window 14 is formed by photoetching. In this way, the surface emitting laser of the present invention shown in FIG. 1(d) is completed.

In this example, the active layer structure is Alo5Gao.
5As/In, 2Gao8As/Alo5Gao, As
Although the single quantum well structure is used, the material and structure are limited to J'', and a multiple quantum well structure or a single layer structure may also be used.

However, in the case of a single layer structure, the disordering effect is weakened, so the layer thickness is preferably 100 OA or less. Furthermore, although a gap layer is used in this embodiment, it is not necessary to provide a gap layer if the concentration near the surface of the second semiconductor multilayer reflective film is made sufficiently high (p>10 cm2). Further, as the semiconductor multilayer reflective film, 670 GaAs/802 AlAs were used, but the invention is not limited thereto.
Other compositions and thicknesses may be used as long as the structure is an alternately laminated structure of /4n2 layers. Further, in this embodiment, a concentric ring pattern is used as the groove pattern around the semiconductor pillar, but the pattern is not limited to this, and a ring pattern of a rectangular or other shape may be used as long as the width of the groove is approximately constant. , the present invention can be effectively applied.

Next, a second embodiment of the present invention will be described in detail with reference to drawing C. FIGS. 2(a) to 2(e) are cross-sectional views for explaining the manufacturing process of one embodiment of the surface-emitting semiconductor laser of the present invention.

First, a 1] type GaAs semiconductor substrate, an n type A] As layer, and an 11 type GaAs layer with a nominal thickness of λ/4n (λ: laser oscillation wavelength determined approximately by the forbidden band width of the active layer; n: each semiconductor layer) n-type layered with about 20 cycles of - Bunko at a rate of 17
+, conductive multilayer reflective film 2, n-type A with a thickness of 500 ~ 17ym, n-type cladding layer 16 of lXGa1-XA5 (x = 0.3-0.7), and N with a thickness of about 100 mm,... Ga,
,,.

As (y=0.05~0.5) tilt well layer and thickness F
Quantum consisting of 30 to 200 GaAs confinement layers
Well active layer 3 and P type A17 with thickness 500 ~ 1/1 m.
Ga1. As (z=0.3-0.7) p-type cladding layer 1
7. How thick is the p-type AlAs layer and p-type GaAs layer? A
/4nr p-type semiconductor multilayer reflective layer alternately stacked for about 10 to 20 cycles 1! p-type GaA with a thickness of 10 to 1000
, s character 1 layer 15 and molecular beam Yu, Pitagishi (MBE
) method, and then SiO on the grown substrate.
, an insulating film such as SiN or a resist film of about 30
00A~5□m was formed 7, and the inner diameter was 1/m~100. /, m, outer diameter approximately 10 μm ~
A donut-shaped region of about 150 μm is removed to form a concentric mask 18. Thereafter, using this mask 18, a dry etching technique such as reactive ion beam etching (RIBE) using C1□ plasma is applied, so that at least the quantum layer 3 is exposed.
Etching is performed until the surface is completely etched to form a pattern 7 (Fig. 2(a)).
).

, -, a cylinder surrounded by this column 7; a second light-emitting region 6 is formed, but this light-emitting region 6 remains without being cosotched across the column 7'! Conductor layer ζ river 5: to: h
Therefore, the stress t2 applied to the light emitting region 6 of the semiconductor (1)
This is significantly reduced by 7 times. Next, 5 becomes a mutual diffusion promoting film.
An insulating film 5 such as 102 or SiN film is formed on the entire 1111 I
5. After that, apply photoresist 19 to the groove 7, which will be filled in. At this time, apply the photoresist 19 to the groove 7.
Since it is extremely small, the resist 19 is almost the same due to its viscosity. It is applied evenly (Fig. 2(b)). Next, a dry etching technique such as anti-irradiation (RIE) using oxygen/ions 20 is used to dry the growth surface until the edge film 5 is exposed. First, remove the resist by notching (FIG. 2(C)). After this, only the L-insulating film 5 exposed on the growth surface is removed by f and J cutting, and then the 1.7 insulating film in the groove is removed.・Remove the cyst by washing. Next, for example, Ga
Heat treatment is performed at 7008C to 900°C using the FJ method, Istwouf JIS method, etc. using an As substrate as a protective substrate.During this step 1, impurities or vacancies are introduced from the insulating film 5. A semiconductor metamorphic layer 8 is formed only in the groove 7, and the quantum I-Fuco active layer 3 on the side surface of the light emitting region 6 is disordered, and the forbidden band width becomes large there, so that a buried structure is effectively formed. (Figure 2(d)). At this time, since the insulating film 5 does not exist on the growth surface, impurities etc. are not introduced from the growth surface, and problems such as reduction in luminous efficiency and r, increase in series resistance, etc. do not occur. Note that the mutual diffusion promoting film and the heat treatment method may be other than those shown in the first embodiment. Thereafter, after forming Au on the entire surface as the p-side electrode 10, the Au is etched away from areas other than the light emitting region by photolithography. Finally, a null electrode Ga is formed on the back surface of the n-type GaAs substrate 1 other than the light emitting region 6.
AuGeNi/AuNi is formed as the As substrate 11, and the surface emitting semiconductor laser shown in FIG. 2(e) is completed. .

In this embodiment as well, the quantum well active layer is a single quantum well, but the present invention is applicable not only to this but also to multiple quantum wells.

The present invention is not limited to this, and the present invention can also be applied to cases where disordering is used by introducing impurities using a Si film, Zn-doped 5OG (Spin-on-Glass), etc., as in the first embodiment.

↓゛In the surface-emitting Rayleigh shown in the two examples,
In both cases, the reactive current can be reduced to more than 1/10 compared to conventional methods.
Oscillation at a low threshold is the main function. In addition, there is no damage during the manufacturing process or mounting, and the product can be manufactured at a high yield.

In two embodiments of the invention the material system is GaAs/Al
Although the material is GaAs-based, it is not limited to this, and other materials such as I
The present invention is also applicable to C in the GaAs/InP system.

(Effects of the Invention) According to the method for manufacturing a surface emitting laser according to the present invention, the reactive current component due to surface angle coupling is almost eliminated, and a surface emitting laser that oscillates at a low threshold current can be manufactured with high yield. Moreover, mechanical stress is less likely to be applied to the light-emitting region, and there is no deterioration of device characteristics or low production process yields.Also, it is easy to form a brainer, and by forming a brainer, it is easy to wire multiple electrodes, and thin wiring is possible. However, since it can be formed well without step breaks, it is suitable for laser arrays and integrated devices.

[Brief explanation of drawings]

FIG. 1(a) to (+i) are J, surface-emitting insteps according to the present invention,
Conductor 1. 3, which is a cross-sectional view showing about 1L of fabrication of the first embodiment of the present invention, and FIGS. , - shows the manufacturing process of the second embodiment of -
It's 9IN. In the figure, 1. . . . semiconductor substrate, 2 . . . first conductivity type cliff conductor multilayer reflection) 191. :3...active layer, 4...
・Second conductivity type semiconductor multilayer anti-reflective film, 5...5102 film, 6. Ban conductor company (light emitting area), 711.
Groove, 8...! 1'-conductor metamorphic layer (disordered region), 9
---8iN film, 1o-p type electric rod, 1F, -n type electrode, 12---T-shaped beam, 13...polyimide, 14...light output height 1° window, 15 ... A Yasobu layer, 16... N-type cladding layer, 17=,, P-type cladding layer, 18...\'Screw, 19... Sotoresist, 20... Oxygen/fO) 3°

Claims (3)

[Claims] (1) At least a semiconductor multilayer reflective film of a first conductivity type, a quantum well active layer having at least one quantum well structure, and a semiconductor multilayer reflective film of a second conductivity type are provided on a semiconductor substrate, and the quantum well 1. A surface-emitting semiconductor laser comprising a semiconductor column serving as a light emitting region surrounded by a groove reaching an active layer, and a metamorphic layer provided on a semiconductor side surface of the groove. (2) Forming on a semiconductor substrate a semiconductor layer comprising at least a semiconductor multilayer reflective film of a first conductivity type, a quantum well active layer having at least one quantum well structure, and a semiconductor multilayer reflective film of a second conductivity type. forming a groove reaching the quantum well active layer by etching to form a semiconductor pillar that becomes a light emitting region surrounded by the groove; and forming an interdiffusion promoting film including at least an insulating film on the semiconductor surface. a step of removing the interdiffusion promoting film by directional dry etching except for the side surfaces of the groove; and a step of performing interdiffusion in the semiconductor layer on the side surfaces of the groove by heat treatment. A method of manufacturing a surface emitting semiconductor laser, characterized in that: (3) A semiconductor layer comprising at least a semiconductor multilayer reflective film of a first conductivity type, a quantum well active layer having at least one quantum well structure, and a semiconductor multilayer reflective film of a second conductivity type, on a semiconductor substrate. forming a groove that reaches the quantum well active layer by etching and forming a semiconductor pillar that becomes a light emitting region surrounded by the groove; and forming an interdiffusion promoting film including at least an insulating film on the semiconductor surface. a step of applying a photoresist on the mutual diffusion promoting film so that the groove becomes flat; a step of removing the mutual diffusion promoting film by etching except for the groove portion; and a step of removing the mutual diffusion promoting film by heat treatment. A method for manufacturing a surface emitting semiconductor laser, comprising the step of performing interdiffusion in the groove to form a semiconductor metamorphic layer.