JPH0332079A - Semiconductor light emitting element and manufacture thereof - Google Patents

Abstract

PURPOSE:To improve heat dissipation characteristics and achieve a long life by providing a buried layer, consisting of a good insulating and high resistance material, to the same level as that of the upper surface of a ridge and forming electrodes on the upper surface thereof. CONSTITUTION:An n-GaAs layer 2, an n-AlGaAs layer 3, a GRIN-AlGaAs layer 4, a quantum well active 5 by a superlattice, and a GRIN-AlGaAs layer 6 are formed on an n-GaAs substrate 1. Further, a p-AlGaAs layer 7, a p<+>-GaAs layer 8 are provided to form a semiconductor wafer. Then, a ridge part is formed by removing the layer 8 and partly the layer 7, excluding the regions of the layers 7, 8 under a mask 10. Thereafter, a buried layer 9 of a high resistance semiconductor material is provided in the lower parts on both sides of the ridge part to about the same level as that of the upper surface of the ridge part. Then, when electrodes 10, 11 are formed on the upper surface of the ridge and on the buried layer 9, a current from the electrode 11 toward the electrode 12 is concentrated in the ridge part. Herein, the buried material of the buried, layer 9 has nearly the same thermal characteristics as GaAs and good heat dissipation characteristics to achieve a long life.

Description

Detailed Description of the Invention Summary of the Invention In a ridge waveguide type semiconductor light emitting device, by using a high resistance semiconductor material (for example α-31) as the material of the buried layer, the heat dissipation characteristics are improved and the life is extended. can be achieved.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor light emitting device and a method for manufacturing the same.

Conventional technology and its problems As a current confinement type semiconductor light emitting device, C3P (Channel
eled 5ubstrate Planar) laser, TJS (Transverse Junction
n 5tripe) Laser, PBR (Polylmj
lasers, etc. The cost and device performance of such a laser are determined by how simple and reliable the process is to manufacture it.

An example of the structure of a C8P laser is shown in FIG. This C8P laser is manufactured by the following manufacturing process.

A stripe-like a26 with a width of about 5 μm is formed on an n-GaAs substrate 21, and an nAIo, aaGao, and e7AS layer 22 is grown thereon so that the entire surface is flat. Next, A l O, o 5Gao, 95AS
Active layer 23. A p-AIcaaGacsyAS layer 24 and an n-GaAs layer 25 are sequentially grown. Thereafter, Zn is diffused into the positions corresponding to the striped grooves 26, and C
A Zn diffusion region is indicated by reference numeral 27) to form a current confinement region. Finally, a p-electrode 28 and an n-electrode 29 are provided on the upper and lower sides.

The csp laser uses the LP method (Llpuld phase e
pItaxy or MOCVD method (Metal-Org
anic Che*1eal Vapor Deposit
tion).

This C8P laser and its manufacturing method have the following drawbacks.

1.) In the LP method, etc., the entire surface of the substrate is lightly etched (light etching) before crystal growth in order to obtain high quality crystal growth. However, with the C8P laser, a fine groove with a width of about 5 μm is machined on the substrate before crystal growth, so if light etching is used, there is a problem that the full corners will be rounded, so the light etching process is omitted. are doing. For this reason, crystal growth is performed without smoothing the substrate surface, making it difficult to obtain high-quality crystals.

2) As mentioned above, LP is used for crystal growth on a substrate with grooves.
Only the MOCVD method or the MOCVD method can be used. However, when trying to grow crystals on the surface of a substrate with grooves using these methods, due to the dependence of the growth rate on the surface orientation, back etching may occur and the shape of the groove bodies may be changed. It changes it.

3) In the Zn diffusion process, it is necessary to accurately align the mask with the groove position, which complicates the process.

4) The Zn diffusion process itself requires accurate temperature control and a long time.

From the above points, there are problems with cost reduction and performance stability.

An example of the structure of a TJS laser is shown in FIG. The manufacturing process of this TJS laser is as follows.

n Alo, 4 Gao, 6 on n-GaAs substrate 31
As layer 32゜n-AI Ga As active layer 3
3. n-^1c4Gao, e Asyl-)' layer 34. p-^1ca Gao, e As layer 35. Then, the n-GaAs layer 36 is sequentially grown. Then p
-Zn diffusion is performed in a predetermined region 37, and finally a p-electrode 39 and an n-electrode 40 are provided. The current injected from the p''-Zn diffusion region 37 flows laterally through the active layer 33 as shown by the arrow, and this becomes a kind of current confinement region and also becomes an oscillation region 38 where laser oscillation occurs.

Since the TJS laser has a structure in which crystals are grown on a flat substrate, the crystal growth itself is easy, but the manufacturing process has the following drawbacks.

5) The Zn diffusion process requires accurate temperature control and a long time.

6) In Zn diffusion, Zn also diffuses in the lateral direction, resulting in lack of position controllability of the 9 oscillation region.

From the above points, there are problems with lower cost and stability of performance.

The PBR laser was proposed by the applicant (for example, Japanese Unexamined Patent Publication No. 83-1221117), and as shown in FIG.
1 As cladding layer 42. GaAs active layer 43
．． p-AlxGa1-, As cladding layer 44. Then, a p''-GaAs cap layer 45 is grown in one process, and a stripe-shaped etching mask 47 with a width of about 5 μm is formed on the cap layer 45 using, for example, photoresist (FIG. 5(a)).Next. Figure 5(b)
In this step, a ridge portion is formed by etching (chemical etching or dry etching) the portions of the cladding layer 44 and the cap layer 45 that are not covered by the mask 47 to the middle of the cladding layer 44. Furthermore, Figure 5 (
In C), after removing the etching mask 47,
A heat-resistant polyimide resin 48 is applied to the entire surface of the semiconductor wafer so thickly that the upper surface becomes flat and cured.

Thereafter, in FIG. 5(d), the resin 48 is removed by ashing using oxygen plasma until it reaches the top of the ridge portion. Finally, as shown in FIG. 5(e), a p-side electrode 49° and an n-side electrode 50 are deposited on the upper and lower parts, respectively.

The upper surfaces of the cap layer 45 and the resin 48 are flush with each other and are flat, and electrodes are formed over the entire upper surfaces thereof. The low-lying parts on both sides of the ridge part are filled with polyimide resin 48.

The electrode 49 is attached to the PBR semiconductor laser thus obtained.
When a current is passed from the electrode 50 toward the electrode 50, the current does not flow in the low-lying parts on both sides of the ridge because of the resin 48, and the current concentrates only in the ridge part. As a result, the active layer 43 below the ridge
Only that part becomes a light emitting part and emits laser oscillation controlled in transverse mode.

Since this PBR laser requires only one growth and etching process, it is possible to reduce the cost.

Furthermore, since crystal growth is performed on a flat substrate and an etching process with excellent controllability is adopted, the device performance is highly stable.

Furthermore, since the top surface on which the ridge is formed is flat,
It is possible to perform so-called junction-down mounting (a mounting method in which the top and bottom are reversed so that the board is facing up, which has good heat dissipation characteristics), and high output can be expected.

However, although the polyimide resin used to fill the ridge has excellent properties in terms of electrical insulation and thermal expansion, its poor thermal conductivity makes it difficult to efficiently release the heat generated in the oscillation region to the outside. I can't. Even if the above-mentioned junction down method is used, the efficiency of heat dissipation does not increase and the life of the element cannot be improved.

SUMMARY OF THE INVENTION The object of the present invention is to improve the heat dissipation characteristics of a PBR laser while maintaining the possibility of cost reduction and the stability of characteristics (high yield), thereby improving the device life.

The present invention provides a ridge-type semiconductor light emitting device, in which a buried layer made of a high-resistance semiconductor material is provided in a low-lying portion on both sides of a ridge portion to a height almost flush with the top surface of the ridge, and electrodes are provided on the top surface of the ridge and the top surface of the buried layer. It is characterized by the formation of

A method of manufacturing a semiconductor light emitting device according to the present invention is as follows.

A ridge portion is formed on a semiconductor wafer, and a polycrystalline or amorphous buried layer made of a high-resistance semiconductor material is formed around the ridge portion so as to bury the ridge portion.

The buried layer is then removed by etching until the upper part of the ridge is exposed, and an electrode is formed thereon.

The high-resistance semiconductor material used for the buried layer has poorer electrical conductivity than the semiconductor wafer, and has a thermal conductivity and coefficient of thermal expansion similar to (preferably within two orders of magnitude) the semiconductor wafer material. , for example, amorphous silicon (α
-8t), zinc sulfur (Zn5), moth, lium antimony (Ga5b), etc. In particular, when the semiconductor wafer is GaAs-based, it is preferable to use α-St, which has very similar physical properties such as lattice constant, and α-3l
is suitable for use due to its high thermal conductivity.

The polycrystalline or amorphous buried layer can be formed using a vapor deposition method, a sputtering method, or the like.

According to this invention, it is possible to obtain a light emitting element that can be placed at a low location and has excellent stability of performance, like the above-mentioned PBR laser. Since a high-resistance semiconductor material such as α-8l is used as the embedding material, heat dissipation characteristics are improved. By improving heat dissipation characteristics, junction-down mounting can be used effectively, and the lifespan of the device can be extended. This junction
In down mounting, a conductive adhesive containing In can also be used.

Since Sl does not allow 1n to adhere, the risk of electrical shorts caused by the adhesive can be reduced.

DESCRIPTION OF THE EMBODIMENTS FIG. 1 is a perspective view showing a ridge waveguide type semiconductor laser according to an embodiment of the present invention, and FIG. 2 shows its manufacturing process. The structure of the semiconductor laser shown in FIG. 1 will become clear by explaining its manufacturing process.
A method of manufacturing this semiconductor laser will be explained with reference to FIG.

As shown in FIG. 2(a), on the n-GaAs substrate 1,
n-GaAs layer 2. n-AlGaAs layer 3. GRIN(
Graded-Index) -AlGaAs layer 4. Quantum well active layer by superlattice 5. GRIN-AlGaAs
Layer 6゜p-AlGaAs layer 7 and p-GaAs layer 8
is grown by a single crystal growth process, and a striped etching mask lO having a width of approximately 5 μm is formed on this semiconductor wafer by a photolithography process. Preferably, this mask IO also serves as an ohmic electrode made of GrAu, for example.

Next, as shown in FIG. 2(b), the p-GaAs layer 8 and the p-AlGaA
The portion of the s layer 7 not covered by the mask IO is p −
The AlGaAs layer 7 is removed halfway to form a ridge portion. Etching is not only chemical etching but also dry etching.
Etching is also acceptable. Further, the width and height of the ridge portion may be determined depending on the desired waveguide mode.

Further, as shown in FIG. 2C, a buried layer 9 made of, for example, α-81 is formed by vacuum evaporation over the entire surface of the semiconductor wafer until the upper surface becomes substantially flat, thereby burying the ridge portion.

Subsequently, as shown in FIG. 2(d), the α-5l buried layer 9 is removed by RIE using CF4 gas until the mask electrode IO is exposed.

Finally, as shown in FIG. 2(e), p-side electrodes (TIPtAu) 11. are placed on the entire upper and lower surfaces, respectively. The process is completed by depositing an n-side electrode (AuGeN1) 12.

The upper surfaces of the α-GaAs layer 8 and the α-8L buried layer 9 are flush and flat, and the electrodes 11 are formed over the entire upper surface.
is formed. The lowland areas on both sides of the ridge are α-St.
It is filled with

The final assembly of individual elements may be performed using a general method.

When a current is passed from the electrodes 11 to 12 in the semiconductor laser device thus obtained, no current flows in the low-lying areas on both sides of the ridge because of the buried layers 9.

Current concentrates only on the ridge. As a result, only the portion of the active layer 5 below the ridge becomes a light emitting portion and oscillates in a transverse mode controlled manner.

α-3i not only has high electrical resistance and good insulation properties, but also has a thermal expansion coefficient and thermal conductivity that are close to the gap between the element materials.
Since it is approximately the same as s, it is possible to improve the heat dissipation characteristics without applying strain stress to the laser element. Therefore, a longer life can be expected.

In the above embodiment, it goes without saying that the p and n conductivity types may all be reversed. Further, the active layer may have a normal double heterojunction structure or a quantum well structure. Furthermore, a distributed feedback type may be used. Semiconductor wafer is G
Needless to say, it is not limited to the aAs type. Furthermore, the present invention is applicable not only to semiconductor lasers but also to light emitting diodes.

[Brief explanation of drawings]

FIG. 1 shows an embodiment of the present invention, and is a perspective view of a ridge type semiconductor laser, and FIGS. 2(a) to 2(e) show the manufacturing process of this semiconductor laser. Figures 3 to 5 show conventional examples, and Figure 3 is a C8
FIG. 4 is a sectional view showing the structure of a P laser, FIG. 4 is a sectional view showing the structure of a TJS laser, and FIGS. 5(a) to 5(e) show the manufacturing process of a PBR laser. 9...α-8l buried layer. LO... CrAu oak electrode and etching mask. 11...p-electrode (TIPtAu) or more

Claims (3)

[Claims] (1) In a ridge-type semiconductor light-emitting device, a buried layer made of a high-resistance semiconductor material is provided on the low-lying portions on both sides of the ridge portion to almost the same height as the top surface of the ridge, and electrodes are provided on the top surface of the ridge and the top surface of the buried layer. A semiconductor light emitting device is formed. (2) Form a ridge on a semiconductor wafer, form a polycrystalline or amorphous buried layer made of a high-resistance semiconductor material around the ridge so as to bury the ridge, and then layer the buried layer until the upper part of the ridge is exposed. A method for manufacturing a semiconductor light-emitting device, in which the electrode is removed by etching and an electrode is formed on top of it. (3) Forming a mask with electrode material on the semiconductor wear,
3. The method of manufacturing a semiconductor light emitting device according to claim 2, wherein the ridge portion is formed by removing the periphery of the mask by etching.