JPS6258692A - Manufacture of semiconductor light emitting device - Google Patents

Abstract

PURPOSE:To improve the controllability of the width of an active layer and to improve the controllability and efficiency for burying high-resistance InP into an etching part formed in a double hetero junction by fabricating a semiconductor layer by a predetermined step. CONSTITUTION:On a p-InP substrate 1, a p-InP buffer layer 2, a p-InP cladding layer 3, a p-InGaAsP active layer 4, an n-InP cladding layer 5, and an n-InP cap layer 6 are laminated in order, after which a tungsten film 7 is vapor- deposited. Next, the film 7 is patterned to form a stripe electrode 8 which is then used as a mask for the mesa etching of the layer 6 to 3. Further, the layer 4 is over-etched. Subsequently, mass transportation is done to bury the active layer 4' by the InP layer 10. After that, the buried layer 11 consisting of InP crystal is epitaxially grown to fabricate a semiconductor laser.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for manufacturing a semiconductor light emitting device, and more particularly to a method for manufacturing a semiconductor light emitting device in which the process of forming a buried layer is improved.

[Conventional pincer technique and problems]

Semiconductor light emitting devices have features common to semiconductor devices such as small size, high efficiency, light weight, and resistance to mechanical imaging, as well as features such as high-speed direct modulation and high efficiency coupling with optical fibers. Therefore, in recent years, it has been put into practical use as a light source for optoelectronics, but in order to further expand its field of use, it is necessary to significantly reduce costs by improving the manufacturing process.

By the way, as one of the semiconductor light emitting devices, in order to have a double heterojunction structure with a crystal of an I[[-V group compound semiconductor and to form a waveguide in a stripe shape, a ■-V group compound semiconductor having a lower refractive index than the active layer is used. An embedded type semiconductor laser is known in which a semiconductor laser is embedded with a semiconductor, and the crystal is further filled with sugar to form a reflecting surface that is perpendicular to the bonding surface. Such semiconductor lasers (InP-based semiconductor lasers) have been conventionally manufactured, for example, by the method described below.

First, a cladding layer made of n-type 1nP, an active layer made of InGaAsP, and a cladding layer made of p-type InP are sequentially laminated on an n-type 1nP substrate to form a double heterojunction. 5i02 pattern is selectively formed.

Subsequently, using the SiO+ pattern as a mask, a double-to-zero junction is mesa-etched to a predetermined depth. Subsequently, p-type and n-type l are formed in the etched area by liquid phase growth.
The buried layer is selectively grown by alternating nP. Next, after removing the SiO2 pattern and forming positive and negative 1ffl on the cladding layer and the back surface of the substrate, sugar is applied in the direction perpendicular to the double heterojunction to form an open plane that will serve as a reflective surface, and the InP cladding is InGaAs layers and buried layers
A buried semiconductor laser is manufactured in which current and light are confined in a P active layer region.

However, since the above-described manufacturing method employs a liquid phase growth method, it lacks mass productivity and has problems in that film thickness controllability is low.

(Objective of the Invention) The present invention enables easy and reproducible control of the width of the active layer, and selectively and efficiently deposits a high-resistance InP crystal layer in the etched portion formed in the double heterojunction. It is an object of the present invention to provide a method for manufacturing a semiconductor light emitting device that can be easily embedded, can use the mask material as it is as an electrode, and has achieved a significant reduction in process steps and improved performance.

[Summary of the invention]

The present invention provides an l having a double heterostructure on an InP substrate.
A step of forming an nP-based semiconductor layer, a step of forming an electrode of a high melting point metal on this semiconductor layer, and selectively removing the semiconductor layer to a desired depth by chemical etching using this electrode as a mask. A process of over-etching the active layer, which is a constituent material of the semiconductor layer, a process of heat-treating in an atmosphere containing phosphorus to fill the over-etched part with InP, and a process of injecting a high-resistance layer into the etched part of the semiconductor layer by vapor phase epitaxial growth. This method is characterized by comprising a step of selectively growing crystals of the 101 layer. According to the present invention, the width of the active layer can be easily and reproducibly controlled as described above, and a high-resistance InP crystal layer can be selectively and efficiently formed in the etched portion formed in the double heterojunction. It is possible to embed the mask material with good controllability, use the mask material as it is as an electrode, and obtain a semiconductor light-emitting device with significantly shortened process steps and improved performance.

[Embodiments of the Invention] Hereinafter, an example in which the present invention is applied to an InP-based buried semiconductor laser will be described in detail with reference to FIGS. 1 to 4.

First, a p-type I film with a thickness of 0.5 μm is placed on a p-type InP substrate 1.
A buffer layer 2 made of nP, a cladding layer 3 made of n-type 1nP with a thickness of 2 μm, and a thickness of 0. 1 μm p-type InGa
After sequentially laminating an active layer 4 made of ASP, a cladding layer 5 made of n-type 1nP with a thickness of 2 μm, and a cap layer 6 made of n-type 1nP with a thickness of 0.2 μm, a thick layer is formed on the cap layer 6 by sputtering. A tungsten film 7 having a thickness of 0.2 μm was deposited (as shown in FIG. 1). Subsequently, after patterning the tungsten film 7 to form a striped electrode 8 having a width of 40 μm or less, the electrodes 8 from the cap layer 6 to the cladding layer 3 are selectively coated with a Br2-methanol solution using the electrode 8 as a mask. Etched portions 9 were formed by mesa etching.

Subsequently, the active layer 4 is over-etched using an etching solution consisting of sulfuric acid, hydrogen peroxide, and water (as shown in Figure 2).

Next, mass transport was performed by exposing the sample to a PH3 atmosphere at a temperature of 700°C. At this time, as shown in FIG. 3, the cladding layers 3 above and below the overetched active layer 4 are formed.
At the same time, the In of No. 5 moved to the overetching area, and the P in the atmosphere was diffused into the overetching area, thereby forming an active layer 4' of a predetermined width filled with the InP layer 10.

Next, hydrogen (carrier gas) at 6000 sccm.

Trimethylindium 7 sec and phosphine 50
A high-resistance InP crystal was grown using a vapor phase epitaxial growth method in which 0 sec of source gas is decomposed at a temperature of 650°C. At this time, as shown in FIG. 4, the InP crystal does not grow at all on the electrode 8 made of tungsten, but selectively grows only on the etched part 9, and the InP crystal is at the same level as the surface of the positive M pole 8. A buried layer 11 was formed.

After this, although not shown, the back surface of the substrate 1 is polished to a desired thickness.
A negative electrode made of an alloy of AU-ae-N+ is formed, and the substrate (wafer) is diced and spread in a direction perpendicular to the length direction of the buried layer 11, and the sugar as a coagulator is formed. A semiconductor laser having a reflective surface was manufactured.

Therefore, according to the present invention, 40μ
After forming a strip-shaped electrode 8 made of tungsten having a width of less than m, and etching the semiconductor layers from the cap layer 6 to the cladding layer 3 using the electrode 8 as a mask, and further over-etching the active layer 4, PH at a given temperature
By performing mass transfer by exposing the active layer 4 to three atmospheres, the overetched portion of the active layer 4 can be filled with an InP layer. As a result, it is active! ! The width of 4' can be easily and accurately controlled, and as a result, a semiconductor laser with a small threshold current can be easily manufactured.

Furthermore, by performing vapor phase epitaxial growth after forming the etched portion 9 by the selective etching, the InP crystal with high resistance is not grown on the electrode 8, and the same InP crystal is selected only for the etched portion 9. The buried layer 11 can be formed. Moreover, in the vapor phase epitaxial growth process, the electrode 8 made of tungsten is
A good ohmic contact is made between the cap layer 6 and the cap layer 6. Therefore, the buried layer 11 can be formed in the etched portion 9 with good controllability and efficiency, and the mask material used for selective crystal growth can be used as it is as a positive electrode, so the process is significantly shortened, and as a result, It becomes possible to mass-produce high-performance semiconductor lasers.

In the above embodiment, tungsten (W) was used as the high melting point metal, but MOLTa, Ti.

Other high melting point metals such as Pt, Re, Ir may also be used. In addition, when depositing such a high melting point metal film, in order to improve the ohmic properties between the electrode formed by patterning the pattern and the InP semiconductor layer, the high melting point metal film may be deposited while mixing a dopant such as MO. Alternatively, a relatively low melting point metal film such as Affi or N1 may be formed as a base for the high melting point metal.

In the above embodiment, in order to improve the reproducibility of semiconductor laser characteristics, the p-type InP buffer layer 2, the n-type InP buffer layer 2,
Although the P cap layer 6 is grown, it is possible to omit this depending on the case. Furthermore, it is of course possible to manufacture a light emitting device using an n-type InP substrate instead of an n-type 1nP substrate.

In the above embodiments, the depth of the etched portion before performing selective vapor phase epitaxial growth may be arbitrary. For example, even if a deep etched portion reaching the substrate is formed, the same effects as in the embodiments can be achieved.

In the above embodiment, an InP-based semiconductor laser has been described, but the present invention can be similarly applied to a light-emitting diode having a buried structure or a surface-emitting type semiconductor laser.

〔Effect of the invention〕

As detailed above, according to the present invention, the width of the active layer can be easily adjusted.
Moreover, it can be controlled with good reproducibility, and moreover, it is possible to selectively and efficiently embed a high-resistance InP crystal layer in the etched portion formed in the double heterojunction with good III-III properties, and furthermore, it is possible to use the mask material as it is as an electrode. It is possible to provide a method for manufacturing a semiconductor light emitting device, which can be used to significantly shorten the process and achieve high performance.

[Brief explanation of the drawing]

1 to 4 are cross-sectional views showing the manufacturing process of a buried semiconductor laser according to an embodiment of the present invention. 1... N-type 1nP substrate (wafer), 2... N-type 1nP buffer layer, 3... N-type 1nP
cladding layer, 4.4” ・I) type 1 nGaAsP
active layer, 5... n-type 1nP cladding layer, 6...
n-type 1nP cap layer, 8... electrode made of tungsten, 9... etching part, 11... high resistance In
A buried layer consisting of P. Applicant's representative Patent attorney Takehiko Suzue C-In ('Q -- CL)\Ding C~

Claims (2)

[Claims] (1) InP with double heterostructure on InP substrate
a step of forming a high-melting point metal electrode on this semiconductor layer, selectively removing the semiconductor layer to a desired depth by chemical etching using this electrode as a mask, and removing the semiconductor layer to a desired depth. A process of over-etching the active layer, which is a constituent material of the layer, a process of heat-treating in an atmosphere containing phosphorus to fill the over-etched part with InP, and injecting high-resistance InP into the etched part of the semiconductor layer by vapor phase epitaxial growth. 1. A method of manufacturing a semiconductor light emitting device, comprising the step of selectively growing crystals of a layer. (2) The method for manufacturing a semiconductor light emitting device according to claim 1, wherein the high melting point metal is tungsten.