JPS62165384A - Manufacture of semiconductor light emitting device - Google Patents

Abstract

PURPOSE:To suppress a leakage current and facilitate reduction of the threshold current of a laser by employing mixed solution of hydrogen bromide, hydrogen peroxide and water or mixed solution of hydrogen bromide, hydrogen peroxide and acetic acid as etchant. CONSTITUTION:An N-type InP buffer layer 2, an InGaAsP active layer 3 and a P-type InP cladding layer 4 are deposited over the whole surface of an N-type InP substrate 1. Then, after an SiO2 mask 11 is formed on the top surface of a region where a mesa structure 5 is to be formed, mixed solution of 20cc of water or acetic acid 4cc (47wt%) of hydrogen bromide and 2cc (31wt%) of hydrogen peroxide is employed for etching both sides of the mask 11 until the active layer 3 is exposed on both sides to form the mesa structure 5. Side surfaces where a (111)A face does not exist are formed under a constricted part of the mesa structure 5, in other words on the sides where the side surface of the active layer 3 are exposed. Then current blocking layers 6 and 7 are deposited. After the mask 11 is removed, insulating layers 8 and electrodes 9 and 10 are formed and the device is completed by cleaving.

Description

[Detailed Description of the Invention] [Summary] In the manufacture of a buried semiconductor light emitting device using an indium phosphorous semiconductor and having an active layer with a band-shaped mesa structure without a double heterojunction, an etching solution used in etching to form the mesa structure is used. By using a mixture of hydrogen bromide, hydrogen peroxide, and water, or a mixture of hydrogen chloride, hydrogen peroxide, and acetic acid, the side surface of the active layer was prevented from becoming the (111) A side. It is something.

[Industrial application field]

The present invention relates to a method of manufacturing an embedded semiconductor light emitting device in which an active +l1 layer forming a double heterojunction is formed into a band-shaped mesa structure using an indium phosphorus semiconductor, and particularly relates to a method of manufacturing the mesa structure.

For example, there are many semiconductor light emitting devices such as BH (Bur
ied Heterostructure) laser, etc.

Lasers such as BH lasers are used as optical signal sources for optical communication and the like because of their relatively small oscillation threshold current, but it is desired to further reduce the oscillation threshold current.

[Conventional technology]

FIG. 3 is a sectional side view of the configuration of the BH laser.

In the figure, 1 is an n-type indium phosphide (lnP) substrate, 2 is an n-type 1nP buffer layer, 3 is an indium gallium arsenide phosphide (InGaAsP) active layer which becomes the emission fi region, and 4 is a p-type 1nP clarifier. 1, 5 is a strip-shaped mesa structure (the longitudinal direction is perpendicular to the drawing) formed by the cladding layer 4, active layer 3, and buffer N2, 6 is a p-type 1nP current 1+L layer, and 7 is a mesa structure. 8 is an insulating layer of silicon dioxide (Si02), and 9 and 10 are metal electrodes.

In this laser, the active layer 3 forms a double heterojunction in the mesa structure 5, and when a current is passed from the electrode 9 to the electrode 10, a reverse P-N junction is formed between the current gate 1F bottom 6 and 7. The current is concentrated in the active layer 3 due to the presence of a forward P-N junction formed between the current stop layer 6 and the buffer layer 2 and having a rising voltage higher than that of the active layer 3.

If the current is increased to a value greater than the value (oscillation threshold current) '1-, laser oscillation occurs and laser light is emitted from the active layer 3.The conventional manufacturing method of this laser is as shown in Fig. 4 (r). Top view (al to IcI).

That is, see Figure (a)], a buffer layer 2 is formed on the entire surface of the substrate 1.
, an active layer 3, and a cladding layer 4 are deposited by, for example, a liquid phase growth method.

Next [see Figure fb], after forming a 5iQ2 mask 11 in the mesa structure 5 formation region on the upper surface, bromine (Brz) was applied.
The mesa structure 5 is formed by etching the active layer 3 using a mixture S of 1 and methanol (CH3011) as an etching solution until the active layer 3 is exposed on the side surface.

Next, as shown in FIG. 1 (see C1), currents 17 and +1-layers 6 and 7 are deposited by, for example, liquid phase growth while leaving the mask 11 as it is.

Next [see FIG. 3], after removing the mask 11, the insulating layer 8, electrodes 9 and IO are formed and folded to complete the process.

[Problem that the invention seeks to solve]

The BH laser manufactured in this way has a mesa structure 5 of i
It becomes chimesa-shaped, and its sides are easily susceptible to heat damage (III
) It has become A. In addition, since bits are generated in the buffer layer 2 etched with the etching solution mentioned above, when the electric current ff, l1ti +) - layer 6 is multiplied by jiff, the ungrown portion 12 as shown in FIG. ga/1: Yes.

For this reason, when a current is applied, a portion of the current that should be concentrated in the active layer 3 becomes the leakage current 1° and I2 as shown in Figure (C1).
Therefore, it no longer contributes to light emission, and there is a problem that the oscillation threshold (11V current increases).

Means for Solving Problem C] The problem described in L is InP phosphorus crystal consisting of m-v group mixed crystal containing indium (In) or III-V group consisting of In and phosphorus (P) as four-part components. A semiconductor plate having a multilayer structure is used, in which an active layer which forms a double heterojunction in contact with a mixed crystal and becomes a light emitting region is provided on a semiconductor substrate. Hydrogen bromide (HRr) and hydrogen peroxide (I2 o2
) and water (I20) and I (Br and H2
This problem is solved by the production method of the present invention, which uses either one of the mixed liquids of O2 and acetic acid (CH3co2H).

[Effect]

The etching solution of type 2ff is used when the side surface is (1) during etching to form the mesa structure 5 shown in
11) This is something that the inventor of the present application has discovered through much experience as a means to prevent the formation of the A-side and to prevent the occurrence of the pits 12 shown in FIG. 4.

The ten effects of this etching solution are such that the material of the active layer 3 in FIG. 3 is an I[IV group mixed crystal containing In,
This includes the case where the material of the buffer layer 2 and the cladding layer 4 is an InP crystal or an m-v group mixed crystal containing In and P as main components.

Therefore, if the etching described in FIG. 4(b) is performed using either of the above two types of etching solutions, the side surfaces of the formed mesa structure 5 can be avoided from becoming (111) planes. Also, the current 11 explained in Figure 4 (C1)
It is possible to avoid the generation of ungrown portions 12 in the deposition of ti +l- layers 6.

This suppresses the occurrence of the leakage currents (1) and (12) mentioned above, and leads to a reduction in the threshold current of the laser.

〔Example〕

Examples of the 4-invention method will be described below with reference to FIGS. 1 and 2.

FIG. 1 is a sectional side view of the first embodiment of the present invention.
+c+, Fig. 2 is a culm forward side sectional view (al~F01) of the second embodiment, and each fat~ (C1 corresponds to (al~fcl) of the conventional method in Fig. 4). Also, the same reference numerals throughout the drawings indicate objects with the same material and the same function.

The manufacturing of the laser according to the embodiment shown in FIG. 1 is as follows.

That is, [see Figure ta+J, n-type In
l' substrate 11 - n-type 1nP buffer layer 2, In
GaAsP active individual 3, p-type 1nP Kuraso FI'pt4,
Tit product. The thicknesses of the buffer layer 2, active layer 3, and crat layer 4 are, for example, approximately 2 μm and approximately 0.15 μm, respectively.
m, approximately 1.5 μm1.

Next, [see Figure fb)], after forming a 5i02 mask 11 in the mesa structure 5 formation region of the A surface, water or acetic acid 20c
c. Using a mixed solution of 4 cc of hydrogen bromide (47%) and 2 cc of hydrogen peroxide solution (31%), both sides of the mask 11 are etched until the active layer 3 is exposed on the sides, forming the shape shown in the figure. A mesa structure 5 is formed. The dimensions of mesa structure 5 are:
For example, for the above thickness of each layer, the width of the mask 11 is about 3
μm, and when the etching depth is approximately 1.8 μm, the width of the top portion is approximately 1.5 μm, the width of the constriction of the crat N4 is approximately 0.8 μm, and the width of the active layer 3 is approximately 1.5 μm. . A side surface where the (111) A plane does not exist is formed below the constriction section 1- of the mesa structure 5, that is, on the side where the side surface of the active N3 is exposed.

Next, refer to Figure c fcl]. *
Deposit m+F layers 6 and 7. In this case, the ungrown portion 12 that occurs in the conventional method does not occur.

Next [see FIG. 3], as in the conventional method, the mask 11 is
After removing, an insulating layer 8, electrodes 9 and 10 are formed and folded to complete the process.

In the thus manufactured laser, the occurrence of the leakage currents 1 and 12 described above is suppressed, and the oscillation threshold current is approximately 1/1 of that of a laser manufactured by the conventional method with the active layer 3 having approximately the same dimensions. It was reduced to 2.

The fabrication of the laser according to the embodiment shown in FIG.
The mesa structure 5 is formed using the same etching solution by replacing the 5102 mask 11 shown in FIG.
e1 As shown in the figure, current blocking layers 6 and 7 and a p-type TnP camp layer 3 are laminated in a layer 11. In this case, as shown in FIG. 1b1, the width of the top of the mesa structure 5 is smaller than that of the first embodiment, the constriction in the cladding layer 4 disappears, and (Ill) A side surface without a surface is formed, and the oscillation threshold current is reduced as in the first embodiment.

Although not shown, the thickness of the crat layer 4 is 0.1,
If an InGaAsP layer of about 11111 is provided, 5i(
12 masks] 1, it is possible to form a mesa structure 5 similar to that of the second embodiment.

Note that in the embodiment described above, the materials of the buffer layer 2, active layer 3, and cladding layer 4 are specified, but the material of the active layer 3 is
If the buffer layer 2 and the cladding layer 4 are each made of InP or an m-v group mixed crystal containing In and P as main components, the same method as in the embodiment is applied. A mesa structure 5 similar to that of the embodiment can be formed using an etching solution.

Furthermore, although the above embodiment has been shown using a BH laser as an example, if the active layer 3 forming a double heterojunction using the above material is provided in the mesa structure 5, it is a buried type semiconductor light emitting device.
It can be easily inferred that the configuration of the present invention is effective.

〔Effect of the invention〕

As explained above, according to the configuration of the present invention, in manufacturing an embedded semiconductor light emitting device having an active layer forming a double heterojunction in a band-shaped mesa structure using an indium phosphorus semiconductor, the side surface of the active layer is (111). It can be prevented from becoming the A-plane, and has the effect of reducing the oscillation threshold current of a BH laser, for example.

[Brief explanation of drawings]

FIG. 1 is a side cross-sectional view of the first embodiment of the present invention (al~
IC1, FIG. 2 is a side cross-sectional view of the second embodiment of the present invention (al~
tel, Fig. 3 is a schematic side view of an example of a BH laser, and Fig. 4 is a cross-sectional side view of the laser shown in Fig. 3 using the conventional manufacturing method.
) ~ fc), In the figure, 1 is the substrate, 2 is the haphazard layer, 3 is the active layer, 4 is the cladding layer, 5 is the mesa structure, 6.7 is the current blocking layer, 8 is the insulating layer, 9, IO is the electrode, 11, lla is the A mask, 12 is an ungrown portion, 13 is a camp layer, 11, and 2 are leakage currents. 3rd @Illustrated laser

Claims (1)

[Claims] An active layer, which forms a double heterojunction in contact with an indium phosphorous crystal made of a III-V group mixed crystal containing indium or a III-V group mixed crystal whose main components are indium and phosphorus, and serves as a light emitting region, is formed on a semiconductor substrate. When forming a band-shaped mesa structure containing the active layer by using a semiconductor plate having a multilayer structure and etching a mask on the upper surface thereof,
A semiconductor light emitting device characterized in that, as an etching solution for the etching, one of a mixed solution of hydrogen bromide, hydrogen peroxide, and water and a mixed solution of hydrogen bromide, hydrogen peroxide, and acetic acid is used. manufacturing method.