JP2005166881A - Nitride semiconductor laser element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a nitride semiconductor laser element without generating lowering of laser light output even when being operated in an atmosphere by suppressing a deposit generated on the emission end face of laser light. <P>SOLUTION: The nitride semiconductor laser element 1 successively laminates a first conductive AlGaN clad layer 4, an active layer 5, and a second conductive AlGaN clad layer 6 on a first substrate 2, and an insulation layer 9 sandwiching a stripe-like second conductive AlGaN clad layer 7. It forms a second conductive GaN contact layer 8 on the second conductive AlGaN clad layer 7 to emit the laser light from the active layer 5. It also forms a protection layer 13 consisting of TiO<SB>2</SB>on both the end faces of the first substrate 2 or the second conductive GaN contact layer 8 at the emission side of the laser light. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a nitride semiconductor laser device capable of obtaining stable laser characteristics even in the atmosphere.

A conventional nitride semiconductor laser element is described in Japanese Patent Application Laid-Open No. 2003-101113.
That is, Patent Document 1 discloses a chip mounting portion that is vertically formed on a stem so as to contact a side surface, a submount fixed to a flat portion of the chip mounting portion that is orthogonal to the stem surface, and the submount. A nitride semiconductor laser element fixed by solder with the n-electrode side facing upward, and the p-electrode side of the nitride semiconductor laser element and the pin of the stem are connected by a wire, and a cap is placed on the stem It is described that nitrogen gas is sealed in the cap.

JP 2003-101113 A (pages 5 to 6, FIGS. 1 to 3)

By the way, a nitride semiconductor has recently been assembled in order to reduce the cost by assembling without the cap or to be assembled into an optical component used in this apparatus when used in an optical disk apparatus. Applications that use laser elements exposed to the atmosphere have increased.
However, when the nitride semiconductor laser element is operated in the atmosphere, there has been a problem that the laser light output is reduced.
This is because the wavelength of the laser light emitted from the nitride semiconductor laser element is from blue to green and short waves, so the photon energy is large, so that the decomposition of gaseous organic substances present in the atmosphere is promoted, and the laser light It is considered that a large amount of precipitates are generated on the end face from which light is emitted.

  Accordingly, the present invention has been made in view of the above problems, and a nitride semiconductor laser that suppresses precipitates generated on the laser light emission end face and does not cause a decrease in laser light output even when operated in the atmosphere. The object is to provide an element.

In the present invention, the first conductive type AlGaN cladding layer, the active layer, the first second conductive type AlGaN cladding layer, and the striped second conductive type AlGaN cladding layer are sandwiched on the first substrate. A nitride semiconductor laser in which a second conductive type GaN contact layer is formed on the second second conductive type AlGaN cladding layer, and a laser beam is emitted from the active layer In the element, a nitride semiconductor laser element is provided, wherein a protective layer made of TiO ₂ is formed on both end faces of the first substrate to the second conductivity type GaN contact layer on the laser beam emission side. To do.

According to the present invention, the protective layer made of TiO ₂ is formed on both end faces of the first substrate and the second conductivity type GaN contact layer on the emission side of the laser beam emitted from the active layer. Thus, a nitride semiconductor laser element capable of stable operation even in the air can be obtained.

A nitride semiconductor laser device according to an embodiment of the present invention will be described with reference to FIGS.
1A and 1B show a nitride semiconductor laser device according to an embodiment of the present invention, in which FIG. 1A is a cross-sectional view and FIG. 1B is a cross-sectional view of MM in FIG.
FIG. 2 is a diagram showing a current test result of the nitride semiconductor laser element.

As shown in FIGS. 1A and 1B, a nitride semiconductor laser device 1 according to an embodiment of the present invention includes an n-type GaN buffer layer 3 having a thickness of 1 μm on an n-type GaN substrate 2 and a thickness. An n-type Al _0.14 Ga _0.86 N clad layer 4 having a thickness of 1.2 μm, an active layer 5 and a p-type Al _0.14 Ga _0.86 N clad layer 6 having a thickness of 0.2 μm are laminated. At the center of the p-type Al _0.14 Ga _0.86 N clad layer 6, a p-type Al _0.14 Ga _0.86 N clad layer 7 having a stripe shape with a width of 1.5 μm and a thickness of 1 μm, and a p-type GaN contact Layer 8 is sequentially laminated.
The striped p-type Al _0.14 Ga _0.86 N clad layer 7 forms a ridge portion.
Here, the active layer 5 has a structure in which an In _0.02 Ga _0.98 N barrier layer having a thickness of 5 nm and an In _0.15 Ga _0.85 N quantum well layer having a thickness of 2 nm are paired, and this is made into 2 to 4 pairs. The structure is sandwiched between undoped GaN guide layers having a thickness of 0.1 μm.

Further, on the p-type Al _0.14 Ga _0.86 N clad layer 6, a pair of insulating layers 9 and 9 are formed with the p-type Al _0.14 Ga _0.86 N clad layer 7 and the p-type GaN contact layer 8 interposed therebetween. A p-type electrode 10 is formed on the striped p-type GaN contact layer 8 and the pair of insulating layers 9, 9, and an n-type electrode 11 is formed on the n-type GaN substrate 2 opposite to the stacking direction. ing.
Further, as shown in FIG. 1A, an optical film is formed on both end surfaces of each layer of the p-type electrode 10 to the n-type electrode 11 in the laser beam emission direction so as to reflect the laser beam with a predetermined reflectance. The multilayer reflective films 12 and 12 are formed by alternately laminating, for example, Al ₂ O ₃ and ZrO ₂ having a thickness of (1/4) λ and different refractive indexes. Here, λ is the wavelength of the laser beam. On the multilayer reflective films 12, 12, protective films 13, 13 made of TiO ₂ are laminated.

The nitride semiconductor laser element 1 causes a forward current to flow from the p-type electrode 10 side to the n-type electrode 11 side, and when this current exceeds the oscillation threshold, the striped p-type Al _0.14 Ga is used. _The laser beam is emitted from the active layer 5 corresponding to the lower part of the _0.86 N clad layer 7.

Next, the nitride semiconductor laser element 1 was energized in the atmosphere, and the decrease in laser light output was examined. The result is shown in FIG.
In FIG. 2, the semiconductor laser element of the present invention is a nitride semiconductor laser element 1, and the conventional semiconductor laser is usually a protective film 13 of the nitride semiconductor laser element 1 instead of TiO _2. This is a conventional semiconductor laser device using Al ₂ O ₃ , SiO ₂ , or Si ₃ N ₄ . The energization current at this time is 50 mA, the horizontal axis is the energization time (time), and the vertical axis is the laser beam output (value normalized by the initial value).
As shown in FIG. 2, in the nitride semiconductor laser device 1, the laser light output is constant even after 3000 hours, whereas in the conventional semiconductor laser device, the laser light output varies periodically. And unstable.

This is considered to be because, in the nitride semiconductor laser element 1 of the embodiment of the present invention, a part of the laser light is absorbed by TiO ₂ , causing a photochemical reaction and making it difficult to attach organic matter to the surface of the protective film 13. .
On the other hand, in the conventional semiconductor laser device, organic matter in the atmosphere is decomposed by the laser light and adheres to the end face, and the increase in the thickness causes light absorption and the reflectance is periodically changed. It is done.

As described above, according to the embodiment of the present invention, since the protective film 13 made of TiO ₂ is provided on the laser light emission surface, a part of the laser light is absorbed by TiO ₂ and causes a photochemical reaction. Therefore, it is difficult to attach an organic substance to the surface of the protective film 13, so that a decrease in laser light output can be prevented.
In the embodiment of the present invention, the protective layer 13 is formed on both end faces of each layer in the p-type electrode 10 to the n-type electrode 11 in the laser beam emission direction. However, each layer in the n-type GaN substrate 2 to the p-type GaN contact layer 8 is used. You may make it form in the both end surfaces.
Further, although TiO ₂ is used for the protective film 13, TiO—N or the like can be used depending on the wavelength of the laser beam. Further, the thickness of TiO _{2 of the} protective film 13 can be set to (1/4) λ to (1/2) λ so that the reflectance of the laser emission surface is optimized.
Further, TiO ₂ having a thickness of 5 nm to (1/4) λ is formed on the multilayer reflective films 12 and 12 in which (1/4) λ Al ₂ O ₃ and ZrO ₂ are alternately laminated. It may be a reflective film.

  It can be widely used for next-generation optical disk devices and medical devices.

1 shows a nitride semiconductor laser device according to an embodiment of the present invention, where (A) is a cross-sectional view and (B) is an MM cross-sectional view of (A). It is a figure which shows the electricity supply test result of a nitride semiconductor laser element.

Explanation of symbols

1 ... nitride semiconductor laser device, 2 ... n-type GaN substrate (first substrate), 3 ... n-type GaN buffer layer, 4 ... n-type Al _0.14 Ga _0.86 N clad layer (first conductivity type AlGaN clad layer), 5 ... active layer, 6 ... p-type Al _0.14 Ga _0.86 N cladding layer (first second conductivity type AlGaN cladding layer), 7 ... p-type Al _0.14 Ga _0.86 N cladding layer (second second conductivity type AlGaN cladding layer) 8 ... p-type GaN contact layer (second conductivity type GaN contact layer), 9 ... insulating layer, 10 ... p-type electrode, 11 ... n-type electrode, 12 ... multilayer reflective film, 13 ... protective film

Claims (1)

A first conductivity type AlGaN cladding layer, an active layer, a first second conductivity type AlGaN cladding layer, and an insulating layer sandwiching the striped second second conductivity type AlGaN cladding layer on the first substrate in order In the nitride semiconductor laser device that is stacked and further formed with a second conductivity type GaN contact layer on the second second conductivity type AlGaN cladding layer, and emits laser light from the active layer,
_2. A nitride semiconductor laser device comprising: a protective layer made of TiO ₂ formed on both end faces of the first substrate to the second conductivity type GaN contact layer on the laser beam emitting side.

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