KR101348493B1 - Laser Diode Structure And Manufacturing Method Thereof - Google Patents

Abstract

The present invention solves the shortcomings of the window structure applied to the fabrication of a laser diode, and unlike the prior art, by selecting a method of restricting diffusion of impurities (Zn) on both reflective surfaces, the conventional breakdown voltage ( It is possible to provide a structure of a laser diode having a breakdown voltage improved from 2V to 12V and a manufacturing method of such a laser diode.

Description

Laser Diode Structure And Manufacturing Method Thereof

The present invention relates to a structure of a laser diode and a method of manufacturing the same, and more particularly, to a structure and a manufacturing method of a laser diode to which the window structure is applied.

The present invention relates to a structure of a laser diode applying the window structure and a method of manufacturing the same.

Laser diodes have the advantage that they can be applied to various fields such as display, gaming, communication, medical, industrial. In particular, high-power products that operate in the tens to hundreds of mW class are attracting attention. However, since the laser diode has a small oscillation area, the optical output density is easily increased during operation, and thus, optical damage (COD, Catastrophic Optical Damage), such as deterioration of the reflective surface, which is a light absorption area, occurs. Will receive. This is shown in FIG. It can be seen that as the degradation progresses through FIG. 1, the operation of the laser diode is restricted, and the increase in the level of optical damage enables the fabrication of a high power laser diode.

In order to solve the above-mentioned disadvantages, a method of avoiding light absorption by fabricating a laser diode higher than the central portion has an energy band gap of the active layer near the reflection surface using a concentration difference of impurities. It became. This is a window structure, which refers to a process of diffusing or injecting impurities (Zn) to an active layer in a predetermined region in order to improve energy band gaps of both reflective surfaces of the laser diode as shown in FIG. 2. Such a structure is called a window structure because the vicinity of the reflecting surface becomes a transparent window. However, if the window structure is implemented in the prior art as shown in FIG. 3, durability against optical damage may be increased, but the breakdown voltage may be lowered. This is shown in Table 1. Table 1 shows the results of the optical damage level and breakdown voltage of the same laser diode depending on the window structure. From Table 1, it can be seen experimentally that the breakdown voltage is only about 1/7, although the optical damage level of the laser diode to which the window structure is applied is increased about 3.1 times compared to the optical damage level of the other laser diode.

division Optical damage level
[mW] Breakdown voltage
[V] Laser Diode with Window Structure 70.1 2.0 Laser diode without window structure 22.6 13.6

Breakdown voltage is a current-voltage characteristic of a diode in which only a small leakage current occurs and a current rapidly increases at a specific voltage when a reverse voltage is applied to a P-N junction as shown in FIG. 2. These yields can be divided into two categories: firstly, Avalanche Breakdown and secondly, Zener Breakdown.

The phenomenon that the breakdown voltage decreases when the window process is applied can be explained by Zener breakdown. As the impurity concentration increases due to the window process, the depletion region becomes narrow in the PN junction and the tunnel effect occurs where the valence band energy becomes the energy of the conduction band. As the probability of movement increases, current flows even at low voltages. In other words, by diffusing impurities in the entire reflecting surface, the tunnel effect occurs in the entire reflecting surface, and as a result, the breakdown voltage of the laser diode to which the window structure is applied is obtained.

The present inventors have found a way to control the window process to solve this problem and completed the present invention.

The present invention is to provide a laser diode structure and a method of manufacturing the same that can improve the breakdown voltage of the laser diode to which the window structure is applied to solve the problems of the prior art.

According to the present invention, in the laser diode to which the window structure is applied, impurities are limited to only a part of the active layer so that the breakdown voltage can be improved.
ZnSiO ₂ layer is provided in the current injection region and the periphery thereof, and the periphery except the current injection region includes an impurity diffusion blocking layer,
A laser diode can be provided in which the width X of the impurity diffusion region satisfies the following inequality, and the centers of X and Y coincide.
Y≤X≤2Y
(X: width of impurity diffusion region, Y: width of current injection region)
In addition, the present invention, in order to diffuse the impurities in the active layer, it is possible to provide a laser diode comprising a ZnSiO ₂ layer having a thickness of 300 to 700 kHz in the current injection region and the periphery thereof.

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In addition, the present invention on the n-GaAs substrate using metal organic chemical vapor deposition (MOCVD),

n-GaAs buffer layer;

n-AlGaInP clad layer;

A multi quantum well active layer in which AlGaInP layers are alternately repeatedly stacked on a GaInP layer;

p-AlGaInP cladding layer;

p-GaInP etch stop layer;

p-AlGaInP cladding layer;

p-GaInP contact layer;

First step of sequentially growing the p-GaAs cap layer:

The second step of forming a current injection region using plasma enhanced chemical vapor deposition (PECVD), photolithography, dry etching and wet etch:

Third step of removing p-GaAs cap layer using photolithography method and wet etching method:

4th step of depositing and etching ZnSiO ₂ using PECVD, photolithography method, dry etching method and sputter:

A fifth step of diffusing impurities (Zn) using rapid thermal annealing (RTA):

Step 6: forming a current confined region using PECVD, photolithography and dry etching:

A seventh step of sequentially depositing Ti, Pt and Au as p-type electrodes using a photolithography method and an electron beam evaporator:

Eighth Step of Polishing n-GaAs Substrate Using Lapping and Polishing:

It is possible to provide a method for manufacturing a laser diode comprising the ninth step of depositing AuGe, Ni, and Au in order as an n-type electrode.

In addition, in the fourth step, in order to limit the diffusion of impurities to a part of the active layer, SiO ₂ is deposited by PECVD, and then the photoresist is removed by a photolithography method. It is possible to provide a method for manufacturing a laser diode characterized in that a portion of the photoresist remains as a second.

In addition, in the fourth step, the present invention may provide a method of manufacturing a laser diode, wherein after the development, the SiO ₂ mask is removed only at the upper end of the current injection region by using a dry etch method.

In another aspect, the present invention provides a method for manufacturing a laser diode, characterized in that for depositing the impurity diffusion ZnSiO ₂ layer to a thickness of 300 ~ 700Å in a fourth step, to limit the diffusion of impurities to a portion of the active layer. can do.

Further, in the present invention, the width X of the impurity diffusion region satisfies the following inequality, and the centers of X and Y coincide with each other.

Y≤X≤2Y

(X: width of impurity diffusion region, Y: width of current injection region)

After laminating the ZnSiO ₂ layer, it is possible to provide a method of manufacturing a laser diode, characterized in that to perform a diffusion heat treatment in a temperature range of 500 ~ 600 ℃.

In addition, the present invention may provide a method for manufacturing a laser diode, characterized in that the heat treatment is performed for 10 minutes to 30 minutes.

According to the present invention, it is possible to solve a phenomenon in which the breakdown voltage is lowered due to zener breakdown (tunnel effect) in manufacturing a laser diode applying the window structure.

1 is a graph showing the current-light output characteristics according to the optical damage progress of a typical laser diode.
2 is a diagram showing the structure of a laser diode to which a general window structure is applied.
3 is a voltage-current graph showing a typical breakdown voltage.
4 is a layered cross-sectional view of a laser diode fabricated in accordance with this embodiment.
Fig. 5 is a layered sectional view showing a MOCVD manufacturing step of a laser diode fabricated in accordance with this embodiment.
6 is a layered cross-sectional view of forming a current injection region of a laser diode fabricated in accordance with this embodiment.
7 is a layered cross-sectional view of a p-GaAs cap layer of a laser diode fabricated in accordance with this embodiment.
8A and 8B are layered cross-sectional views after development for removing a PR mask of a laser diode fabricated in accordance with this embodiment.
9A and 9B are layered cross-sectional views after removing a SiO ₂ mask for depositing ZnSiO ₂ of a laser diode fabricated in accordance with this embodiment.
10 is a layered cross-sectional view after ZnSiO ₂ deposition of a laser diode manufactured according to the present embodiment.
11 is a layered cross-sectional view after ZnSiO ₂ diffusion of a laser diode fabricated in accordance with this embodiment.
Fig. 12 is a layered cross sectional view after current limiting region, polishing and electrode forming process of a laser diode fabricated in accordance with this embodiment.
FIG. 13 is a scanning electron microscope photograph showing an impurity diffusion region of a laser diode fabricated by applying a window structure according to the prior art. FIG.
14 is a scanning electron microscope photograph showing the impurity diffusion region of the laser diode fabricated by applying the window structure according to the present embodiment.

Hereinafter, with reference to the accompanying drawings a preferred embodiment of a laser diode structure and a manufacturing method according to the present invention as described above will be described in detail.

Example: Fabrication of 680 nm Laser Diode

1) 0.5 μm of n-GaAs buffer 120 on n-GaAs substrate 110, n- (Al _0.80 Ga _0.20 ) _0.51 In _0.49 P cladding layer 130 2.0 μm using MOCVD, and AlGaInP layer on GaInP layer GaInP / AlGaInP multi-quantum well active layer 140 alternately repeated, p- (Al _0.80 Ga _0.20 ) _0.51 In _0.49 P clad layer 150 0.3μm, p-Ga ₅₁ In _0.49 P etch stop Layer 160 90 p, p- (Al _0.70 Ga _0.30 ) _0.51 In _0.49 P clad layer 170 1.0 μm, p-Ga ₅₁ In _0.49 P contact layer 180 0.05 μm, p-GaAs cap layer 190 0.3 μm To grow sequentially to produce a state as shown in Figure 5 (see Figure 5).

2-1) After depositing 0.6 μm of SiO ₂ using PECVD, an SiO ₂ etching mask 200 is formed on the region where the current injection region is to be formed using a photolithography method.

2-2) The current injection region is formed by etching up to the etch stop layer 160 using an inductively coupled plasma (ICP) and hydrochloric acid solution (see FIG. 6).

3) 0.3 μm of the p-GaAs cap layer 190 is removed using a photolithography method and a sulfuric acid solution (see FIG. 7).

4-1) After deposition of 0.3 μm of SiO ₂ using PECVD (see FIG. 8A), photoresist is removed using a photolithography method. At this time, the development is performed in a time range of 30 to 60 seconds, preferably 45 seconds, so that only a part of the PR is removed and a part remains as shown in FIG. 8B.

4-2) Etch 0.3 μm of SiO ₂ using RIE (Reactive Ion Etcher), which is a dry etching equipment (see FIGS. 9A and 9B).

4-3) All the remaining PRs are removed by development, and ZnSiO ₂ is preferably deposited in a thickness range of 300 to 700 GPa, preferably 500 GPa using a sputter (see FIG. 10).

5) The diffusion thermal annealing (RTA) is used to conduct diffusion heat treatment of impurities (Zn) in a temperature range of 500 to 600 ° C. and a time range of 10 to 30 minutes, preferably at about 550 ° C. for about 20 minutes ( See FIG. 11). The impurity (Zn) can be diffused to the depth of the active layer 140 under the control of the RTA process temperature and time, and the impurity (Zn) cannot be diffused in the region where the SiO ₂ remains (horizontal direction), and the intended region Only impurity Zn diffuses.

6) After depositing 0.12 μm of Si ₃ N ₄ using PECVD, a current limiting region is formed by etching Si ₃ N ₄ other than the current injection region through a photolithography method (see FIG. 12).

7) Ti, Pt, and Au are sequentially deposited to 300, 600, and 10,000 Hz as the p-type electrode 240 using a photolithography method and an electron beam (e-beam) evaporator (see FIG. 12).

8) The n-GaAs substrate is polished to 100 μm using lapping and polishing (see FIG. 12).

9) As the n-type electrode 250, AuGe, Ni, and Au were deposited in order of 800 Å, 200 Å, and 2,500 Å in thickness (see Fig. 12).

The scanning electron microscope photograph of the laser diode manufactured according to the method of the present embodiment is shown in FIG. 14, and the scanning electron microscope photograph of the laser diode manufactured according to the prior art is shown in FIG. 13 to enable mutual comparison. Compared with FIG. 13, it can be seen from FIG. 14 that the diffusion region of impurities is limited, and in addition, the inequality of Y ≦ X ≦ 2Y presented above is also satisfied.

Table 2 shows the electro-optical characteristics of the laser diode manufactured according to the present embodiment in comparison with the laser diode manufactured according to the prior art. It can be seen from Table 2 that the breakdown voltage has improved from 2V to 12V. In particular, no other deterioration was found and only breakdown voltage was significantly improved.

As a result, when the laser diode is fabricated by applying the window structure according to the present embodiment, it is possible to obtain a product having improved optical damage and breakdown voltage, and thus it is possible to expect an effect that can satisfy various requirements of customers.

division Threshold current
[mA] Operating current
[mA] Operating voltage
[V] Optical damage
[mW] Breakdown voltage
[V] Prior art 18.7 34.0 2.42 70.1 2.0 In this embodiment 18.5 34.2 2.41 68.7 12.6

The rights of the present invention are not limited to the embodiments described above, but are defined by the claims, and those skilled in the art can make various modifications and adaptations within the scope of the claims. It is self-evident.

110: n-GaAs substrate 120: n-GaAs buffer 120
130: n- (Al _0.80 Ga _0.20 ) _0.5 1In _0.49 P Clad Layer
140: multi quantum well active layer
150: p- (Al _0.80 Ga _0.20 ) _0.51 In _0.49 P Clad Layer
160: p-Ga ₅₁ In _0.49 P etch stop layer
170: p- (Al _0.70 Ga _0.30 ) _0.51 In _0.49 P Clad Layer
180: p-Ga ₅₁ In _0.49 P Contact Layer
190: p-GaAs cap layer
200: SiO ₂ etching mask
240: p-type electrode
250: n-type electrode

Claims (9)

In the laser diode to which the window structure is applied, impurities are diffused only to a part of the active layer so that the breakdown voltage can be improved.
ZnSiO ₂ layer is provided in the current injection region and the periphery thereof, and the periphery except the current injection region includes an impurity diffusion blocking layer,
The width X of the impurity diffusion region satisfies the following inequality, and the centers of X and Y coincide.
Y≤X≤2Y
(X: width of impurity diffusion region, Y: width of current injection region) delete The laser diode according to claim 1, further comprising a ZnSiO ₂ layer having a thickness of 300 to 700 kW in the current injection region and its periphery to diffuse impurities into the active layer. On an n-GaAs substrate using metal organic chemical vapor deposition (MOCVD),
n-GaAs buffer layer;
n-AlGaInP clad layer;
A multi quantum well active layer in which AlGaInP layers are alternately repeatedly stacked on a GaInP layer;
p-AlGaInP cladding layer;
p-GaInP etch stop layer;
p-AlGaInP cladding layer;
p-GaInP contact layer;
First step of sequentially growing the p-GaAs cap layer:
The second step of forming a current injection region using plasma enhanced chemical vapor deposition (PECVD), photolithography, dry etching and wet etch:
Third step of removing p-GaAs cap layer using photolithography method and wet etching method:
4th step of depositing and etching ZnSiO ₂ using PECVD, photolithography method, dry etching method and sputter:
A fifth step of diffusing impurities (Zn) using rapid thermal annealing (RTA):
Step 6: forming a current confined region using PECVD, photolithography and dry etching:
A seventh step of sequentially depositing Ti, Pt and Au as p-type electrodes using a photolithography method and an electron beam evaporator:
Eighth Step of Polishing n-GaAs Substrate Using Lapping and Polishing:
and a ninth step of sequentially depositing AuGe, Ni, and Au as an n-type electrode. The method of claim 4, wherein in the fourth step, in order to limit diffusion of impurities to a portion of the active layer, SiO ₂ is deposited using PECVD, and then the photoresist is removed by a photolithography method. And a portion of the photoresist is left for 60 seconds. 5. The method of claim 4, wherein in the fourth step, the SiO ₂ mask is removed only after development, only at the upper end of the current injection region by dry etching. 6. The method of claim 4, wherein in the fourth step, in order to limit the diffusion of impurities to a portion of the active layer, a ZnSiO ₂ layer that diffuses impurities is deposited to a thickness of 300 to 700 mW. The method of claim 5, wherein the width X of the impurity diffusion region satisfies the following inequality, and the centers of X and Y coincide with each other:
Y≤X≤2Y
(X: width of impurity diffusion region, Y: width of current injection region)
After laminating the ZnSiO ₂ layer, the method of manufacturing a laser diode characterized in that to perform a diffusion heat treatment at a temperature range of 500 ~ 600 ℃. The method of claim 8, wherein the heat treatment is performed for 10 minutes to 30 minutes.

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