KR100277942B1 - Semiconductor laser diode manufacturing method - Google Patents

Abstract

The present invention relates to a method for manufacturing a semiconductor laser diode, AlGaAs based on the first and second LPE process after mesa formation during the manufacture of a double-channeled-plane Burier Heterostructure (DC-PBH) semiconductor laser diode using an AlGaAs-based material In order to exclude the oxidizing properties of the material, inverse mesas are formed to form mesas, and the mesas are formed by removing the mesas using the melt-back characteristic of LPZ. The continuous formation of the n-type and n-type semiconductor layers and the second cap layer prevents oxidation, which is a problem when manufacturing a DC-PBH semiconductor laser using an AlGaAs-based material, thereby making a semiconductor laser diode of a DC-PBH structure even with an AlGaAs-based material. It was made possible.

Description

Semiconductor laser diode manufacturing method

1 (a)-(d) are sectional views of a conventional semiconductor laser diode manufacturing process of a DC-PBH structure.

2 (a)-(f) are sectional views of a semiconductor laser diode manufacturing process of the DC-PBH structure of the present invention.

* Explanation of symbols for main parts of the drawings

1 substrate 2 nitride film

2a: nitride film pattern 3: reverse mesa portion

4: nitride film pattern interval 5: first cladding layer

6: active layer 7: second cladding layer

8: first cap layer 8a: portion to be removed

9: Mesabu 10: ditch

11: first semiconductor layer 12: second semiconductor layer

13 second cap layer 14 current limiting portion

15: lower electrode 16: upper electrode

The present invention relates to a semiconductor laser diode, and in particular, solves the problem of axial wall oxidation, which is a problem when fabricating a double channeled-flam buried heterostructure (DC-PBH) structure in an Al _x Ga ₁ - _x A _s system. The present invention relates to a method for manufacturing a semiconductor laser diode, which is suitable for use.

Hereinafter, the prior art will be described with reference to the accompanying drawings.

1 (a)-(d) show a process cross-sectional view of a conventional semiconductor laser diode. As shown in FIG. 1 (a), InGaAsP is used on a semiconductor substrate (p-InP) 21 with a thickness of 0.1 μm. After forming the active layer 22, the first cladding layer 23 is formed thereon as n-InP.

The first cladding layer 23, the active layer 22, and the semiconductor substrate 21 are etched by the photo-etching process as shown in FIG. 1 (b), and two trenches 24 having a wide upper portion and a narrow lower portion are fixed. Formed at intervals, a mesa 25 having a wide bottom layer and a narrow upper portion is formed of a semiconductor substrate 21, an active layer (1.5 μm in width) 22, and a first cladding layer 23 between grooves. .

Subsequently, the N-type semiconductor layer 26 and the P-type semiconductor layer 27 are sequentially formed on the exposed surface using InP as shown in FIG. 1 (c), and then the P-type semiconductor layer 27 and the mesa 25 are formed. The second cladding layer 29 is formed as an N-type semiconductor layer (InP) layer on the first cladding layer 23 and the current limiting portion 28, and the N-type InGaAsP is laminated as LPE on the cladding layer 29. To form a cap layer 30.

Then, upper and lower electrodes 31 and 32 are formed on the upper and lower surfaces of the substrate as shown in FIG. 1 (d). However, the pair of current limiting portions 28 is an N-type semiconductor layer 26 and a P-type adjacent to the mesa 25 including the active layer 22 and the intermediate cladding layer 23 in the double trench 24. The semiconductor layers 27 are formed by laminating them in order.

In the conventional laser diode having such a structure, when a positive voltage is applied to the upper and lower electrodes 31 and 32, the mesa including the active layer 22 and the intermediate clad layer 23 at a constant threshold current is applied. An electric current flows to 25, and the carrier is concentrated on the active layer 22 to emit light.

At this time, a PNPN type thyristor is simultaneously formed from the semiconductor substrate 21, the current limiting portion 28, and the second cladding layer 29 to form the n-type semiconductor layer 26 and the P-type semiconductor layer of the current limiting portion 28. The boundary of (27) is reverse biased to become a current blocking layer that prevents main current leakage.

In this conventional technique, after forming a mesa, an N-type semiconductor layer, a P-type semiconductor layer, a second cladding layer, and a cap layer are sequentially formed in the lamination trench and the mesa area by using an LPE device, wherein the primary LPE and the secondary LPE are formed. The side of the mesa is exposed to the air in the process to form an oxide film on this area, which makes it difficult to grow the secondary semiconductor layer and at the same time, even if it grows, the interface is not good later. difficult to create, and Al _x Ga ₁ - _x a _s is the layer due to the severe oxidation process difficulties of - _x a _s system is to implement a laser having a DC-PBH structure of a material of the Al _x G _a1.

The present invention has been made to solve the problems of the prior art, the object of the present invention is to improve the interfacial properties by preventing the oxidation of the mesa portion in the LPE process.

Hereinafter, with reference to the accompanying drawings an embodiment of the present invention as follows.

2 (a)-(f) show a process cross-sectional view of a semiconductor laser diode for explaining the present invention. First, as shown in FIG. 2 (a), PECVD (Plasma Enhenced CVD) on an n-type GaAs semiconductor substrate 1 is shown. A nitride film (Si ₃ N ₄ ) 2 is formed to a thickness of about 200 μs and then a nitride film pattern 2a having a thickness of 7 μm and separated by 2 μm is formed by a photo-etching process as shown in FIG. H ₂ SO ₄ : H ₂ O ₂ : CH ₄ (CH ₂ ) = 1: 2: 7 The upper part of the n-type GaAs semiconductor substrate 1 which is not masked with the nitride film pattern 2a by etching in the (011) direction An inverted mesa portion 3 having a width of 7 μm, a width of 4 μm of the lower portion, and a height of 3.0 μm is formed.

Subsequently, the first cladding layer 5 having a thickness of 1.5 μm and N-Al _{0.14 with} N-Al _0.46 Ga _0.55 As by LPE (Liquid Phase Epitaxy) method on the substrate on which the mesa portion 3 is formed as shown in FIG. 2 (c). an active layer (6) of 0.1μm thick _{Ga 0.8 as, p-Al 0.46} Ga 0.55 as forming a first cap layer (8) of 0.2μm thick second cladding layer 7 and the p-GaAs 1.2μm in thickness in order to do.

That is, the LPE process is continuously formed in the reactor in order.

Then, after removing the nitride film pattern (2a) remaining on the reverse mesa portion (3), as shown in the second (d), the surface of the surface of the solution with a solution of NH ₄ CH: H ₂ O ₂ : H ₂ O = 1: 1: 1 After etching for a second, the GaAs layers of the reverse mesa portion 3 on both sides of the mesa portion 9 made of (5-8) were loaded by etching using a melt-back characteristic of the LPE. It forms a double trench 10 such as a structure.

After removing the first cap layer 8 on the mesa portion 9 as shown in FIG. 2 (e), the first semiconductor layer (p-Al _0.45 Ga _0.55 As) 11 and the second semiconductor layer (n-Al _0.46 ) are removed. Ga _0.55 As) 12 and a second cap layer (p-GaAs) 13 are formed in portions except the mesa portion 9.

At this time, the growth time of the (11-13) layer is 60 seconds, 90 seconds, 60 seconds so that the layer (11-13) is not grown on the upper side of the mesa portion (9).

14 is a current limiting part.

Subsequently, as shown in FIG. 2 (f), the upper electrode 16 is formed on the second cap layer 13 by using Au-Ge.Ni/Au as the n-type electrode, and the p-type electrode is formed under the semiconductor substrate 1. As a result, the lower electrode 15 is formed using Mo / Au.

Therefore, by fabricating the laser diode in this manner, the oxidation problem caused by air exposure of the mesa portion 9, which is a problem in manufacturing a conventional laser diode of the DC-PBH structure, is eliminated and the interface problem is reduced.

The operation of the semiconductor laser diode thus manufactured is as follows.

When a positive (+) (-) voltage is applied to the upper and lower electrodes, current flows to the mesa portion 9 so that holes flow from the second cladding layer 7 and electrons flow from the first cladding layer 5 into the active layer 6. Power generation and amplification at the current outputs the laser light.

At this time, the current limiting portion 14 is composed of the first semiconductor layer 11, the second semiconductor layer 12, the second cap layer 13 and the semiconductor substrate 1 to form an NPNP type thyristor, the current is mesa portion (9) It is prevented from leaking out and light emission occurs at low threshold current and at the same time, it is wrapped in the upper, lower, left, and right side of the active layer 6 with a band gap larger than the active layer 6 and having a lower refractive index. Guiding takes place, enabling high power oscillation in a single mode.

The semiconductor laser fabricated by the above manufacturing process has a mesa part 9 by exposing the substrate to air between the first LPE process and the second LPE process, which have been a problem in the process of manufacturing a conventional laser diode of DC-PBH structure. Secondary LPE growth was difficult due to oxidation, and it acts as a resistance source due to the defect of the interface after fabrication, which makes it difficult to increase the output power by using the melt-back method, which is a characteristic of LPE. By forming the mesa structure in the reactor, the mesa part is exposed to air and the second LPE is used to solve the problem of the oxide film formation and the interface problem of the prior art, thereby making it possible to manufacture a more reliable and high power laser diode. The semiconductor laser manufactured by this technology can be used for optical communication and laser beam printer (LBP) because it can be stable single type, lateral mode and high output oscillation. It works.

Claims (4)

After the nitride film 2 is formed on the semiconductor substrate 1, a process of forming two nitride film patterns 2a having a width of 7 μm and having a width of 2 μm, the semiconductor not masked by the nitride film pattern 2a Etching the substrate 1 to form two reverse mesas 3, the first cladding layer 5, the active layer 8, the second cladding layer 7, and the first cladding on the entire surface exposed after the step. After forming the cam layer 8 in sequence and removing the remaining nitride film pattern 2a, the reverse mesa portion 3 is melt-backed with LPE (liquid phase), and the P-type semiconductor layer is formed. (11), a step of sequentially forming the n-type semiconductor layer 12, the second cap layer 13, after the step, the semiconductor laser diode manufacturing, characterized in that the upper and lower electrodes (15, 16) are formed on the upper and lower portions of the substrate Way. The etching of the semiconductor substrate 1 according to claim 1, wherein the etching of the semiconductor substrate 1 is performed in the (011) direction with a solution of H ₂ SO ₄ : H ₂ O ₂ : CH ₄ (OH) ₂ = 1: 2: 7 Method for manufacturing a semiconductor laser diode, characterized in that. The method of claim 1, wherein the formation time of the p-type semiconductor layer 11, the n-type semiconductor layer 12, and the second cap layer 14 is 60 seconds, 90 seconds, and 60 seconds, respectively. . The method of manufacturing a semiconductor laser diode according to claim 1, wherein after removing the nitride film pattern 2a, the surface of the device is etched with NH ₄ OH: H ₂ O ₂ = 1: 1: 10 solution for 15 seconds to remove the oxide film. .