JPH0157514B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a semiconductor light emitting device, and more particularly to a method for manufacturing a double heterojunction semiconductor light emitting device having a buried structure.

A buried structure is widely used in semiconductor lasers to improve their luminous efficiency.

The conventional method used to form a double heterojunction semiconductor laser with such a buried structure is, for example, indium, gallium, arsenic, phosphorus (InGaAsP).
In the case of an InP-based buried semiconductor laser, first, as shown in FIG.
The first layer is made of N-InP and has a thickness of about [μm].
The cladding layer 2 is made of N-type indium gallium arsenic phosphorus (N-
an active layer 3 made of P-type indium-phosphorous (P-InP) having a thickness of 1.5 [μm] or more;
P-type indium gallium with a thickness of about
A first contact layer 5 made of arsenic/phosphorus (P--InGaAsP) is epitaxially grown one after another.

Next, a striped silicon dioxide (SiO ₂ ) mask pattern is formed in a desired region on the first contact layer 5, and then the epitaxial layer is anisotropically etched, as shown in FIG. 1b. As shown, the first cladding layer 2, the active layer 3, the second cladding layer 4, and the first contact layer 5 are laminated in this order from the bottom to form a mesa stripe 7 having an SiO ₂ mask pattern 6 on the upper surface. .

Next, as shown in FIG. 1c, while the mesa stripes 7 are covered with the SiO ₂ mask pattern 6, the activation of the mesa stripes 7 is selectively applied to the periphery of the mesa stripes 7 on the substrate. a third cladding layer 8 of P-InP reaching the layer 3; a fourth cladding layer 9 of N-InP reaching the top surface of the second cladding layer 4 of the mesa stripe 6;
P-InGaAsP reaching SiO ₂ mask pattern 6
A buried structure was formed by epitaxially growing a second contact layer 5' consisting of the following layers. However, in the selective liquid phase growth method as described above, the epitaxial layer grown on the substrate surface has a tendency to grow thicker in the vicinity of the mesa stripes 7 and thinner in areas separated from the mesa stripes 7. There is a mesa stripe 7 as in the conventional method above.
When the mesa stripe is formed to have a high height of about 5.5 to 6 [μm], the third cladding layer 8, the fourth cladding layer 9, and the second cladding layer are formed to bury the mesa stripe.
Because the growth thickness of the contact layer 5' is larger, the second
A large step is formed on the upper surface of the contact layer 5' as shown in the figure, and as shown in FIG.
After the SiO ₂ mask pattern 6 is removed, the surface of the P electrode 10 continuously formed on the first contact layer 5 and the second contact layer 5' is not flat.

On the other hand, semiconductor lasers generate a large amount of heat during operation, and increasing the heat dissipation efficiency is extremely important for improving their performance. An up-side-down construction in which the electrodes are brazed to the heat sink is preferred.

However, in semiconductor laser chips formed by the conventional method as described above, the P electrode has large irregularities on its surface, which makes it difficult to braze to the heat sink, and it is difficult to braze uniformly. . Therefore, the heat dissipation efficiency of the semiconductor laser chip decreases, and at the same time, heat is not dissipated uniformly from the entire surface of the P electrode, resulting in a sharp temperature distribution within the chip, which may cause the chip to break during operation due to thermal distortion. .

Therefore, in conventional embedded semiconductor lasers, the substrate is made as thin as possible, and the electrodes on the substrate side, such as the N electrode, are brazed to a heat sink to radiate heat from the substrate side. Many methods are used to eliminate the distribution, but in this type of structure, the limit on how thin the substrate can be is about 100 [μm], so the thermal resistance is significantly higher than that of an up-side-down structure, and therefore the heat dissipation effect is poor. This has led to a decrease in the light emission output of the semiconductor laser, a decrease in the operating ambient temperature limit, and a decrease in the life of the device.

In view of the above-mentioned problems, the present invention provides a method for manufacturing a buried semiconductor light emitting device, which flattens the upper surface of the epitaxial layer and enables up-side-down chip mounting.

That is, the present invention provides a method for manufacturing a buried double heterojunction semiconductor light emitting device, in which a first cladding layer, an active layer, and a portion of a second cladding layer are sequentially and successively liquid-phase epitaxially deposited on a semiconductor substrate. a step of etching a mesa stripe consisting of a part of the second cladding layer, an active layer, and the first cladding layer using a mask; using the mask as a growth prevention mask;
burying the mesa stripe by sequentially growing two different conductive cladding layers on the sides of the stripe by liquid phase epitaxial growth; The method is characterized by comprising a step of successively growing the remaining part of the second cladding layer and the contact layer, which is thicker than the second cladding layer, by liquid phase epitaxial growth.

The present invention will be explained in detail below using process cross-sectional views of an embodiment shown in FIGS. 2a to 2f.

For example, in order to manufacture an InGaAsP-InP-based buried semiconductor laser using the method of the present invention, first, as shown in Figure 2a, the (001) plane is mainly grown using the usual sliding liquid phase growth method. N-InP as a surface
A first cladding layer 2 made of N-InP with a thickness of about 5 [μm], an active layer 3 made of N-InGaAsP with a thickness of about 0.1 to 0.2 [μm], and the active layer are formed on a substrate 1. Minimum thickness that can be completely covered e.g.
A portion 4a of the second cladding layer made of P--InP and having a thickness of about 0.2 to 0.3 [μm] is successively epitaxially grown.

Next, after depositing a SiO ₂ film with a thickness of about 1000 [Å] on the substrate by a method such as sputtering,
Using a conventional photolithographic method, a stripe having a desired dimension is formed on the substrate along the in-plane direction [110] or [1 1 0] direction of the substrate as shown in FIG. 2b. A SiO ₂ mask pattern 6 is formed.

Next, the substrate surface is etched with the SiO ₂ mask using an anisotropic etching solution made of bromine, methanol, etc.
Using the pattern 6 as a mask, mesa etching is performed until the width of the active layer 3 reaches a desired width of, for example, about 2 to 3 [μm], and as shown in FIG. A mesa stripe 7' is formed of the first cladding layer 2, the active layer 3 and a part 4a of the second cladding layer and having a SiO ₂ mask pattern 6 on its upper surface.

Next, as shown in FIG. 2d, the mesa stripe 7' is grown using a sliding liquid phase epitaxial growth method on the periphery of the mesa stripe 7' while the SiO ₂ mask pattern 6 is still deposited. Third cladding layer 8 consisting of P-InP reaching the active layer 3 and N-InP reaching the SiO ₂ mask pattern 6
A fourth cladding layer 9 consisting of is selectively formed to embed the mesa stripes.

The third cladding layer 8 and the fourth cladding layer 9 have not only a lateral optical confinement function but also a current blocking function since a PN junction 11 is formed between the two layers.

In the method of the present invention, the height of the mesa stripes that must be embedded is at most 2.5 to 3.
It is about [μm], which is half compared to the conventional method.
The step 12 formed on the upper surface of the fourth cladding layer 9 after the above-mentioned buried growth is significantly smaller than that of the conventional method.

Next, after removing the SiO ₂ mask pattern 6 using hydrofluoric acid (HF) or the like, as shown in FIG. The remaining part 4b of the second cladding layer made of InP and P--InGaAsP of about 0.5 to 1.5 [μm]
A contact layer 5 consisting of the following is continuously grown using a sliding liquid phase epitaxial method. When the growth is completed, the small step 12 that was formed on the upper surface of the fourth cladding layer 9 at the time when the embedding is completed is almost completely removed from the remaining portion 4b of the second cladding layer and the contact layer 5. Almost completely absorbed, the upper surface of the contact layer 5 becomes flat.

Next, as shown in FIG. 2f, a layer of gold (Au), for example, with a thickness of about 3000 Å is deposited on the entire surface of the contact layer 5 of the substrate by a method such as sputtering.
After depositing a zinc (Zn) alloy layer and performing alloying at a temperature of about 300 to 350 [°C] to form the P electrode 10, the entire surface of the back N-InP substrate 1 is coated with a method such as sputtering. For example, a gold (An)-tin (Sn) alloy layer having a thickness of about 3000 [Å] is deposited using the above method, and alloyed at a temperature of about 200 to 250 [° C.] to form the N electrode 13.

Then, the substrate is cut and separated to form a semiconductor laser chip, and the P electrode 10 of the semiconductor laser chip is brazed onto a heat sink using, for example, indium solder to form an up-side-down structure. A buried semiconductor laser is formed, and since the P electrode of the semiconductor laser chip formed by the method of the present invention is deposited on the contact layer 5, which is formed flat as described above, a flat surface is formed. This allows uniform brazing over the entire surface of the heat sink. Therefore, in a semiconductor laser in which a semiconductor laser chip formed by the method of the present invention is mounted in an up-side-down manner, heat is uniformly dissipated from the entire surface of the P electrode on the epitaxial layer to the heat sink. As a result, heat dissipation efficiency is extremely excellent, and at the same time, extreme temperature distribution does not occur within the semiconductor laser chip during operation, and chip breakage does not occur.

In the above embodiments, the present invention was applied to InGaAsP-
Although the InP-based semiconductor laser has been described, the method of the present invention is applicable to GaAlAs-GaAS-based and
It can also be applied to AlGaAsSb-GaSb-based semiconductor lasers and light emitting devices.

As explained above, according to the method of the present invention, it is possible to provide an embedded semiconductor light-emitting device with an up-side-down structure that has an extremely excellent heat dissipation effect. Temperature limits, operating life, etc. are greatly improved, and at the same time, reliability is also greatly improved.

[Brief explanation of drawings]

1A to 1D are process sectional views of a conventional semiconductor laser manufacturing method, and FIGS. 2A to 2F are process sectional views of an embodiment of the semiconductor laser manufacturing method of the present invention. In the figure, 1 is N-type indium phosphorus (N-
InP) substrate, 2 is the first cladding layer, 3 is the active layer, 4 is the second cladding layer, 4a is a part of the second cladding layer, 4b is the remainder of the second cladding layer, 5
is a contact layer or a first contact layer,
5' is the second contact layer, 6 is the SiO ₂ mask pattern, 7 and 7' are the mesa stripes, 8 is the third cladding layer, 9 is the fourth cladding layer, 10 is the P electrode, and 11 is the P electrode. -N juncture, 12 represents a step, and 13 represents an N electrode.

Claims (1)

[Claims] 1. In a method for manufacturing a buried double heterojunction semiconductor light emitting device, a first cladding layer, an active layer and a part of a second cladding layer are successively formed on a semiconductor substrate. a step of performing liquid phase epitaxial growth; a step of etching a mesa stripe consisting of a part of the second cladding layer, the active layer and the first cladding layer using a mask; using the mask as a growth blocking mask; burying the mesa stripe by successively growing two different conductive cladding layers on the sides of the mesa stripe; 1. A method for manufacturing a semiconductor light emitting device, comprising the step of successively growing the remaining part of the second cladding layer and the contact layer, which is thicker than the partially grown second cladding layer, by liquid phase epitaxial growth.