JPH1041585A - Manufacture of group iii nitride semiconductor laser diode - Google Patents

Abstract

PROBLEM TO BE SOLVED: To elongate the life of an element by raising the specular degree at the end face of the resonator of a laser diode, and preventing the light absorption at the end face, and suppressing the rise of element temperature. SOLUTION: To form the electrode to the lower layer of a laser diode 100, etching to expose a part of the lower layer by etching a part of the upper layer is performed, and then electrodes in the upper layer and the lower layer are made, and then the dry etching by the RIBE(reactive ion beam etching) for formation of the end face of a resonator is performed. Wet etching is performed by KOH or the like to the end face after that. Hereby, the damaged layer at the end face made by dry etching is removed, consequently the specular degree of the end face rises, and the light absorption is suppressed. Therefore, the rise of element temperature is suppressed, and the life of the element is elongated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a laser diode using a group III nitride semiconductor. In particular, it relates to a method for forming an end face of a laser-diode resonator.

[0002]

2. Description of the Related Art Heretofore, there has been known an element formed of a gallium nitride compound semiconductor (AlGaInN) on a sapphire substrate to form a blue light emitting diode (LED) or a blue laser diode (LD). In order to efficiently reflect and oscillate the light of the laser diode (LD), it is necessary to keep the perpendicularity and parallelism of the cavity end face high. Cleavage is preferably used to form the resonator end face with high precision. However, in the above-described device, cleavage is difficult because the substrate and the device layer are formed of different materials. For this reason, an end face is formed by dry etching.

[0003]

However, when the end face of the resonator is formed by dry etching as described above,
As a result, the end face is damaged by ions to generate defects, light is absorbed at the end face, and heat is generated at the end face due to light absorption. As a result, there is a problem that the temperature of the element rises and the element deteriorates.

The present invention has been made to solve the above problems, and an object of the present invention is to improve the surface mirrorness of a cavity facet of a laser diode and prevent light absorption at the facet. The purpose is to prevent the temperature of the element from rising and to prolong the life of the element.

[0005]

The feature of the invention for achieving the object is that a p-type nitride semiconductor made of a group III nitride semiconductor is formed on a substrate.
In a method for manufacturing a group III nitride semiconductor laser diode having a layer and an n layer, each layer made of a group III nitride semiconductor is formed on a substrate, and each layer is dry-etched to form an end face of the resonator. The dry-etched end face is wet-etched with an etchant. As a result, since the damage given to the cavity end face by dry etching is removed by wet etching, the specularity of the end face is improved, and light absorption at the end face is prevented. Therefore, the heat generation of the element is prevented, so that the life of the element is prolonged.

The group III nitride semiconductor is preferably Al _x Ga _Y
In _1-XYN (0 ≦ X ≦ 1,0 ≦ Y ≦ 1,0 ≦ X + Y ≦ 1), whereby a blue short-wavelength laser diode can be obtained. In particular, by using a semiconductor laser diode as a cladding layer made of Al _x1 Ga _1-x1 N and an active layer made of In _x2 Ga _1-x2 N, blue laser output can be improved. In addition, the end face can be efficiently formed by using the reactive ion beam etching (RIBE) as the dry etching. Further, desirably, reactive ion beam etching is performed using Cl ₂ gas, so that etching with a high etching rate can be performed. As a desirable wet etching after the dry etching, an etching solution of KOH or NaOH can be used. This makes it possible to efficiently remove the destruction layer generated by dry etching of the resonator end face, and to improve the mirror finish of the end face.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described based on specific embodiments. The present invention is not limited to the following examples. In FIG. 1, a laser diode 10
No. 0 has a sapphire substrate 1 on which a buffer layer 2 of AlN of 500 ° is formed. On the buffer layer 2, a film thickness of about 2.2 μm
m, an electron concentration 2 × 10 ¹⁸ / cm ^3, Si concentration 4 × 10 ¹⁸ / cm high carrier concentration comprising a silicon-doped GaN of ³ n ⁺ layer 3, a thickness of about 1.0 [mu] m, an electron concentration 2 × 10 ¹⁸ / cm ³ , Si concentration 4 × 10 ¹⁸ / c
An n-conductivity type cladding layer 4 made of m ³ silicon-doped Al _0.08 Ga _0.92 N, an active layer 5 made of In _0.08 Ga _0.92 N having a thickness of about 0.05 μm, a thickness of about 1.0 μm, and a hole concentration of 5 × 10 ¹⁷ / c
m ³ , Al doped with magnesium at a concentration of 1 × 10 ²⁰ / cm ³
_A p-type cladding layer 61 made of _0.08 Ga _0.92 N, a contact layer 62 made of magnesium-doped GaN having a thickness of about 0.2 μm, a hole concentration of 7 × 10 ¹⁷ / cm ³ and a magnesium concentration of 2 × 10 ²⁰ / cm ³ are formed. Is formed. Then, an SiO ₂ layer 9 is formed on the contact layer 62, and an electrode 7 made of Ni that is joined to the contact layer 62 through the window of the SiO ₂ layer 9 is formed. Further, an electrode 8 made of Ni is formed on the high carrier concentration n ⁺ layer 3 to be joined to the layer 3. In order to prevent a short circuit between the electrode 7 and the electrode 8, the groove 1 is used.
0 is formed.

Next, the laser diode 100 having this structure will be described.
A method of manufacturing the device will be described. Each layer is sequentially formed on the sapphire substrate 1 of the wafer as shown in FIG. The laser diode 100 was manufactured by vapor phase growth using a metal organic compound vapor phase epitaxy method (hereinafter, referred to as "M0VPE"). The gas used was NH ₃ and carrier gas H ₂ or
N ₂ and trimethyl gallium _{(Ga (CH 3) 3)} ( hereinafter referred to as "TMG") and trimethylaluminum _{(Al (CH 3) 3)} ( hereinafter "TM
A)), trimethylindium (In (CH ₃ ) ₃ ) (hereinafter referred to as “TMI”), silane (SiH ₄ ) and cyclopentadienyl magnesium (Mg (C ₅ H ₅ ) ₂ ) (hereinafter “ CP ₂ Mg ”)
It is.

First, a 100-400 μm-thick single-crystal sapphire substrate 1 whose main surface is an a-surface cleaned by organic cleaning and heat treatment is mounted on a susceptor placed in a reaction chamber of an MOVPE apparatus. Next, the sapphire substrate 1 was subjected to gas phase etching at a temperature of 1100 ° C. while flowing H ₂ at a flow rate of 2 liter / min at normal pressure into the reaction chamber.

[0010] Next, by lowering the temperature to 400 ° C., and H ₂
20 liter / min, NH ₃ 10 liter / min, TMA 1.8 × 10 ^-5
Supplying at mol / min, an AlN buffer layer 2 was formed to a thickness of about 500 °. Next, the temperature of the sapphire substrate 1 was set to 1150
° C, H ₂ at 20 liter / min, NH ₃ at 10 liter / min,
TMG was supplied at 1.7 × 10 ⁻⁴ l / min, and silane diluted to 0.86 ppm with H ₂ gas was supplied at 200 ml / min for 30 minutes to obtain a film thickness of about 2.2 μm.
[mu] m, an electron concentration ^{2 × 10 18 / cm 3,} Si concentration 4 × 10 ¹⁸ / cm high carrier concentration of GaN of silicon doped of the ³ n ⁺ layer 3
Was formed.

Next, the temperature of the sapphire substrate 1 is maintained at 1100 ° C., N ₂ or H ₂ is 10 liter / min, and NH ₃ is 10 liter / min.
Min, TMG 1.12 × 10 ^-4 mol / min, 0.47 × 10 ^-4 mol / min TMA, and, 0.86 ppm diluted silane 10 × 10 ^-9 mol / min to the H ₂ gas, 60 minutes Supplied, an n-conductivity type cladding layer 4 made of silicon-doped Al _0.08 Ga _0.92 N having a film thickness of about 1 μm, an electron concentration of 2 × 10 ¹⁸ / cm ³ and a Si concentration of 4 × 10 ¹⁸ / cm ³
Was formed.

Subsequently, the temperature is maintained at 850 ° C. and N ₂ or H ₂
20 liter / min, NH ₃ 10 liter / min, TMG 1.53 × 10
^-4 mol / min and 0.02 × 10 ^-4 mol / min of TMI supplied for 6 minutes to form an active layer 5 of 0.05 μm In _0.08 Ga _0.92 N.
Was formed.

Subsequently, the temperature is maintained at 1100 ° C. and N ₂ or H ₂
20 liter / min, NH ₃ 10 liter / min, TMG 1.12 × 10
^-4 mol / min, 0.47 × 10 ^-4 mol / min of TMA and CP ₂ Mg
Was introduced at 2 × 10 ^-4 mol / min for 60 minutes to form a p-type cladding layer 61 of magnesium (Mg) -doped Al _0.08 Ga _0.92 N having a thickness of about 1.0 μm. The concentration of magnesium in the cladding layer 61 is 1 × 10 ²⁰ / cm ³ . In this state, the cladding layer 61 is still an insulator having a resistivity of 10 ⁸ Ωcm or more.

Subsequently, the temperature is maintained at 1100 ° C. and N ₂ or H ₂
20 liter / min, NH ₃ 10 liter / min, TMG 1.12 × 10
^-4 mol / min and CP ₂ Mg at a rate of 4 × 10 ^-4 mol / min
This was introduced for 4 minutes to form a contact layer 62 made of GaN doped with magnesium (Mg) and having a thickness of about 0.2 μm. The magnesium concentration of the contact layer 62 is 2 × 10 ²⁰ / cm ³ . In this state, the contact layer 62 still has a resistivity
It is an insulator of 10 ⁸ Ωcm or more.

Next, the contact layer 62 and the cladding layer 61 were uniformly irradiated with an electron beam using an electron beam irradiation apparatus.
Electron beam irradiation conditions are: acceleration voltage of about 10 KV, sample current of 1 μ
A, beam moving speed 0.2mm / sec, beam diameter 60μmφ,
The degree of vacuum is 5.0 × 10 ⁻⁵ Torr. By the irradiation of the electron beam, the contact layer 62 and the cladding layer 61 respectively
Hall concentration 7 × 10 ¹⁷ / cm ³ , 5 × 10 ¹⁷ / cm ³ , resistivity 2Ωc
m, 0.8 Ωcm p-type semiconductor. Thus, a wafer having a multilayer structure was obtained.

Next, as shown in FIG.
An SiO ₂ layer 9 having a thickness of 2000 ° was formed on the sample ₂ by sputtering, and a photoresist 11 was applied on the SiO ₂ layer 9. Then, as shown in FIG. 3, on the contact layer 62, the electrode formation site A and the trench B formation site B for the high carrier concentration n ⁺ layer 3 are formed by photolithography, as shown in FIG.
Of the photoresist 11 was removed. Next, the SiO ₂ layer 9 not covered with the photoresist 11 was removed with a hydrofluoric acid-based etchant.

Next, the contact layers 62 at the portions A and B which are not covered by the photoresist 11 and the SiO ₂ layer 9,
The cladding layer 61, the active layer 5, and the cladding layer 4 were set at a vacuum of 0.
Dry etching was performed by supplying BCl ₃ gas at a rate of 10 ml / min at 04 Torr and a high frequency power of 0.44 W / cm ² , followed by dry etching with Ar. In this step, as shown in FIG. 4, a hole A and a groove 1 for taking out an electrode from the high carrier concentration n ⁺ layer 3 are formed.
0 was formed.

Next, the contact layer 6 of the remaining SiO ₂ layer 9
In 2 of the top coating of photoresist, it performs a photolithography process, a wet etching, as shown in FIG. 5, a window 9 in the electrode formation region of the contact layer 62 of SiO ₂ layer 9
A was formed.

Next, Ni is uniformly deposited on the entire upper surface of the wafer, a photoresist is applied, a photolithography process is performed,
After the etching step, as shown in FIG. 6, the electrodes 8, 7 for the high carrier concentration n ⁺ layer 3 and the contact layer 62 are formed.
Was formed.

Next, dry etching for forming a resonator end face was performed as follows. A photoresist is uniformly applied on the entire upper surface of the wafer, and a resist mask is formed by photolithography with a width of the length of the resonator (y-axis direction).
A strip shape along the x-axis direction is left along the axial direction. Then, the SiO ₂ layer 9 and the electrodes 8 and 7 were left by the resist mask by the width of the resonator length (y-axis direction).
In this state, as shown in FIG.
A resist mask 12 covered along the axis is formed.

Next, Cl at a vacuum of 1 mTorr and a high frequency power of 400 W
_Two gases were supplied at a rate of 6 ml / min, and the windows not covered with the resist mask 12 were dry-etched by reactive ion beam etching (RIBE) until the sapphire substrate 1 was exposed. Thereafter, using the resist mask 12 as a mask, the wafer having the above structure was immersed in a KOH solution heated to a temperature of 50 ° C., and the dry-etched end face was wet-etched for about 2 minutes. Then, after removing the resist mask 12, cleaning was performed with pure water. In this way, as shown in FIG. 7, a resonator end face S of the active layer 5 having a high degree of perpendicularity to the substrate 1 and a high degree of parallelism between the end faces was obtained. Further, as a result of the removal of the damage layer due to the RIBE on the cavity facet S by wet etching, light absorption at the facet can be prevented, the oscillation threshold current value decreases, and the temperature rise of the element can be suppressed. Thus, the device life can be prolonged.

Next, in order to protect the cavity facet S, a multilayer film of SiO ₂ and TiO ₂ was deposited on the cavity facet S by sputtering.

Thereafter, the wafer processed as described above is replaced with x
The wafer is scribed in the axial direction, die-synced in the shape of a strip along the length direction (y-axis) of the laser cavity, and each strip is pressed and cut in the x-axis direction using a scribe groove. Was obtained.

The laser diode 10 thus obtained
In the case of 0, the drive current was 1000 mA, the emission output was 10 mW, and the oscillation peak wavelength was 380 nm. In the laser diode having this structure, as shown in FIG. 1, since the electrodes 7 and 8 are formed on the same plane, the laser diode can be mounted face down on a heat sink on a lead frame. Therefore, since the heat radiation effect is high, the laser output can be improved and the element life can be improved.

In the above embodiment, an alkaline solution such as a NaOH solution may be used for the wet etching, in addition to the KOH solution. In addition, BCl _3, SiCl _{4, and} CCl ₄ can be used as the reactive gas of RIBE in addition to Cl ₂ . further,
The dry etching may be reactive ion etching (RIE) or ion beam assisted etching (IBAE) in addition to RIBE.

The active layer 5 was composed of In _0.08 Ga _0.92 N and the cladding layers 4 and 61 were composed of Al _0.08 Ga _0.92 N. However, the general formula: Al _x Ga _Y In _1-XY N (0 ≦ X ≦ 1, 0 ≤Y ≤1,0 ≤X + Y ≤1)
Any of the binary, ternary and quaternary Group III nitride semiconductors represented by At this time, the composition ratio between the active layer and the cladding layer may be selected so that the band gap of the active layer is narrower than the band gap of the cladding layer and the lattice constant is matched when a double hetero junction is formed. . When an arbitrary quaternary Group III nitride semiconductor is used, the band gap and the lattice constant can be independently changed, so that a double heterojunction having the same lattice constant in each layer can be realized. Although it is desirable to form a double heterojunction, the present invention is not limited to a double heterojunction, but may be a single heterojunction, a homojunction, or the like. A structure may be adopted.

In the above embodiment, the mask in the etching step at the time of forming the electrode 8 has etching resistance to dry etching, such as a metal and a resist, in addition to SiO ₂ . Any material that can be selectively etched or peeled can be employed. Further, although a photoresist is used as a mask in the enchanting step for forming the cavity end face, the lower electrodes 7 and 8 have etching resistance to dry etching of SiO ₂ or the like.
In contrast, any material that can be selectively etched or peeled can be used.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a configuration of a light emitting diode according to a specific embodiment of the present invention.

FIG. 2 is a sectional view showing a manufacturing process of the laser diode of the embodiment.

FIG. 3 is a sectional view showing the manufacturing process of the laser diode of the embodiment.

FIG. 4 is a sectional view showing a manufacturing process of the laser diode according to the embodiment.

FIG. 5 is a sectional view showing the manufacturing process of the laser diode according to the embodiment.

FIG. 6 is a perspective sectional view showing the manufacturing process of the laser diode of the same embodiment.

FIG. 7 is a perspective sectional view showing the structure of the laser diode of the same embodiment.

[Explanation of symbols]

100 laser diode 1 sapphire substrate 2 buffer layer 3 high carrier concentration n ⁺ layer 4 cladding layer (n layer) 5 active layer 61 cladding layer (p layer) 62 contact layer 7, 8 metal electrode 9: SiO ₂ layer 12: Photoresist

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Shiro Yamazaki, 1 Ochiai Nagahata, Kasuga-cho, Nishi-Kasugai-gun, Aichi Prefecture Inside Toyoda Gosei Co., Ltd. Inside Toyoda Gosei Co., Ltd. (72) Inventor Masayoshi Koike 1 Ogataai Nagahata, Kasuga-machi, Nishi-Kasugai-gun, Aichi Prefecture Inside Toyoda Gosei Co., Ltd. 72) Inventor Hiroshi Amano 2-104 Yamanote, Nagoya-shi, Nagoya, Aichi

Claims (6)

[Claims] 1. A method of manufacturing a group III nitride semiconductor laser diode in which a p-layer and an n-layer made of a group III nitride semiconductor are formed on a substrate, wherein each layer made of a group III nitride semiconductor is formed on the substrate. A method of manufacturing a group III nitride semiconductor laser diode, comprising dry-etching each of the layers to form an end face of the resonator, and wet-etching the dry-etched end face with an etching solution. 2. The method according to claim 1, wherein the group III nitride semiconductor is Al _x Ga _Y In.
_{2. The} method of manufacturing a group III nitride semiconductor laser diode according to claim 1, wherein _1-XYN (0 ≦ X ≦ 1,0 ≦ Y ≦ 1,0 ≦ X + Y ≦ 1). 3. 3. The method of claim 1, wherein the dry etching is reactive ion beam etching (RIBE).
3. The method for manufacturing a group III nitride semiconductor laser diode according to item 1. 4. The reactive ion beam etching,
Method for producing a group III nitride semiconductor laser diode according to claim 1, characterized in that the etching using Cl ₂ gas. Wherein said semiconductor laser diode is Al _x1 Ga
Method for producing a group III nitride semiconductor laser diode according to claim 1, characterized in that it comprises a _1-x1 cladding layer consisting of N and an active layer made of In _x2 Ga _1-x2 N. 6. The method according to claim 1, wherein the wet etching is performed with an etching solution of KOH or NaOH.