JPH0794828A - Method for manufacturing semiconductor laser in buried structure - Google Patents

Abstract

PURPOSE:To manufacture a semiconductor laser in buried structure which shows improved oscillation characteristics in a simple manufacturing process within a wide range (mesa structure, growth conditions), is not affected by the change in growth conditions, etc., have an improved reproducibility, and has a high yield. CONSTITUTION:Se-doped n-type InP buffer layer 3, undoped InGaAsP activated layer 4, and p-type InP clad layer 5 are grown on n-type InP substrate 1 by MOVPE and mesa stripe structure is grown in <011> direction by the photolithography and selective etching. Further, p-type InP current block layer 6 and Se-doped n-type InP current concealment layer 7 are deposited on the entire surface of the n-type InP substrate 1 by MOVPE and then the surface of the n-type InP substrate 1 is etched for enabling the p-type InP current block layer 6 to appear only on the upper surface of the mesa stripe. Then, p-type InP overclad layer 8 and p-type InGaAsP cap layer 9 are deposited on the p-type InP current block layer 6 and the n-type InP current confinement layer 7.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a buried structure semiconductor laser using a metal organic chemical vapor deposition method.

[0002]

2. Description of the Related Art Usually, in order to manufacture a semiconductor laser having a low threshold current and a high efficiency, it is necessary to form a buried structure. Generally, in order to form a buried structure by a metal organic chemical vapor deposition method, it is necessary to form a mesa stripe including an active region having a selective growth mask in the upper part and to form a mesa stripe by selective growth. It gets complicated. In order to simplify the laser manufacturing process, a technique for embedding a mesa structure having an active layer without using a selective growth mask is important.

FIG. 4 is a perspective view of steps for explaining a semiconductor laser disclosed in, for example, Japanese Patent Application No. 3-285470 and its manufacturing method. Referring to FIG.
As shown in (a), an n-type InP buffer layer 3, an undoped InGaAsP active layer 4 and a p-type InP clad layer 5 are grown on a (100) plane n-type InP substrate 1 by a metal organic chemical vapor deposition (MOVPE) method. To do.

Next, as shown in FIG. 4B, a mesa structure having a stripe width of 1.5 μm and a height of about 1.0 μm is formed in the <011> direction by photolithography and selective etching.

Next, as shown in FIG. 4C, the p-type InP current blocking layer 6 and the Se-doped n-type InP current confinement layer 7 are grown by using the MOVPE method. At this time, n type I
When the Se doping concentration of the nP layer 7 is 8 × 10 ¹⁸ cm ⁻³ or more, the growth of the n-type InP layer 7 on the upper part of the mesa structure is completely suppressed, and the n-type InP layer 7 is not deposited on the upper part of the mesa structure. It has a layered structure in which the p-type InP layer 6 is exposed. Further, since the n-type InP layer 7 remains except the upper portion of the mesa structure, the p-type InP layer 6 and the n-type InP layer 7 act as a current confinement layer and a light confinement layer with respect to the active layer of the mesa structure.

Next, as shown in FIG. 4D, a p-type InP overclad layer 8 and a p-type InGaAsP cap layer 9 are formed.
To grow.

The device manufactured as described above does not require a step of performing buried growth using a selective growth mask, and a buried structure laser device can be manufactured by a simple manufacturing process.

[0008]

In the method of manufacturing the buried structure semiconductor laser described above, the growth rate of the n-type semiconductor doped with the group VI dopant is mesa based on the experimental results shown in FIGS. 5 (a) and 5 (b). It takes advantage of the difference between the upper part of the structure and the place away from the mesa. However, if the mesa shape, size, growth conditions, etc. change, the growth of the n-type semiconductor layer above the mesa structure cannot be completely suppressed (see FIG. 5). If the n-type semiconductor layer grows on the upper part of the mesa structure (portion A in FIG. 4), the device resistance increases and the oscillation characteristics of the semiconductor laser deteriorate. Therefore, the reproducibility of the oscillation characteristics due to the limitation of the applicable element structure due to the limitation of the mesa structure or the change of the growth condition,
There is a problem that the yield decreases.

Therefore, the present invention has been made to solve the above-mentioned conventional problems, and its purpose is to:
An object of the present invention is to provide a method of manufacturing a buried structure semiconductor laser capable of manufacturing a buried structure semiconductor laser exhibiting good oscillation characteristics in a wide range (mesa structure, growth condition) by a simple manufacturing process. Another object of the present invention is to provide a method of manufacturing a buried structure semiconductor laser capable of manufacturing a buried structure semiconductor laser with good reproducibility and high yield without being affected by changes in growth conditions and the like. It is in.

[0010]

In order to achieve such an object, the method of manufacturing a buried structure semiconductor laser according to the present invention has an active region on an n-type (100) III-V group compound semiconductor substrate <011. The first step of forming a mesa stripe in the> direction, a p-type semiconductor current blocking layer, and a predetermined concentration of VI on the entire surface of the semiconductor substrate by metal organic chemical vapor deposition.
A second step of depositing an n-type semiconductor current confinement layer doped with a group element, and a third step of etching the semiconductor substrate surface so that the p-type semiconductor current block layer appears only on the upper surface of the mesa stripe. , A fourth step of depositing a p-type semiconductor overclad layer and a p-type semiconductor cap layer on the p-type semiconductor current blocking layer and the n-type semiconductor current confinement layer.

Another method of manufacturing a buried structure semiconductor laser according to the present invention comprises a first step of forming a mesa stripe in the <011> direction on an n-type (100) III-V group compound semiconductor substrate, and a semiconductor A second step of depositing an active layer, a p-type semiconductor current blocking layer, and an n-type semiconductor current confinement layer doped with a predetermined concentration of group VI element on the entire surface of the substrate by metalorganic vapor phase epitaxy, and etching the semiconductor substrate surface And a third step of processing so that the p-type semiconductor current block layer appears only on the upper surface of the mesa stripe, and p
A fourth step of depositing a p-type semiconductor overclad layer and a p-type semiconductor cap layer on the n-type semiconductor current blocking layer and the n-type semiconductor current blocking layer.

A method of manufacturing the above-mentioned buried structure semiconductor laser will be described below. In order to completely suppress the growth of the n-type layer on the mesa by the above-mentioned method, the mesa shape, size, and allowable range of growth conditions are narrowed (for example, mesa width W1.1 μm shown in FIG. 5, Se concentration, Se concentration). Of 8 × 10 ¹⁸ cm ⁻³ or more when embedded with n-type InP). However, even if the growth of the n-type layer cannot be completely suppressed, it is possible to realize a sufficient film thickness difference between the n-formed long layer in the upper part of the mesa structure and the n-formed long layer in the other region. For example, as shown in FIG. 5, even if the mesa width W is wide and about 3.5 μm, if the group VI dopant concentration is 8 × 10 ¹⁸ cm ⁻³ or more, and if the mesa width W is about 1.1 μm. , VI
When the group dopant concentration is 5 × 10 ¹⁸ cm ⁻³ or more, the growth rate of n-type InP on the mesa is suppressed to 1/2 or less,
A sufficient difference in film thickness from other regions can be realized. Therefore, after growing up to the n-type layer, by etching the entire surface, only the n-type layer on the mesa can be removed to expose the p-type layer on the surface. Therefore, after that, by forming the p-type over cladding layer and the cap layer on the entire surface of the substrate, the element resistance is small, and a structure capable of sufficiently blocking the current can be formed in the portion other than the mesa region. Further, since the entire surface of the substrate is etched, the etching process does not require pretreatment such as patterning and can be easily performed by etching using an etching gas in the reaction furnace.

[0013]

According to the method of manufacturing a buried structure semiconductor laser of the present invention, the buried structure semiconductor laser can be manufactured by a simple manufacturing process without the step of performing the buried growth using the selective growth mask. Further, in the step of depositing the n-type semiconductor current confinement layer, it is not necessary to completely suppress growth on the mesa, and high reproducibility and yield can be realized under a wide range of manufacturing conditions.

[0014]

Embodiments of the present invention will now be described in detail with reference to the drawings. (Embodiment 1) FIGS. 1A to 1E are perspective views of steps for explaining an embodiment of a method for manufacturing a buried structure semiconductor laser according to the present invention. In the figure, as shown in FIG. 1A, the film thickness d = on the (100) plane n-type InP substrate 1.
A 1.0 μm Se-doped n-type InP buffer layer 3, an undoped InGaAsP active layer 4 with a film thickness d = 0.1 μm, and a p-type InP clad layer 5 with a film thickness d = 0.3 μm are M
It grows by the OVPE method.

Next, as shown in FIG. 1B, a mesa structure having a stripe width of about 1.5 μm and a height of about 1.0 μm is formed in the <011> direction by photolithography and selective etching.

Next, as shown in FIG. 1C, a Zn-doped p-type InP current block layer 6 having a film thickness d = 0.8 μm and a Se-doped n-type InP film having a film thickness d = 1.0 μm are formed by using the MOVPE method. The current confinement layer 7 is grown. At this time, n type I
The Se doping concentration of the nP current confinement layer 7 is set to 5 × 10.
^{When it is 18} cm ⁻³ or more, the growth of the n-type InP current confinement layer 7 on the upper part of the mesa structure is suppressed, and the thickness of the n-type InP current confinement layer 7 other than that is deposited on the upper part of the mesa structure to be less than about ½. do not do.

Next, as shown in FIG. 1D, hydrogen chloride gas is flown into the reaction tube to etch the entire growth surface by about 0.5 μm. At this time, the growth of the n-type InP current confinement layer 7 is suppressed on the upper portion of the mesa structure, and the film thickness thereof is about 0.5 μm or less, so that the p-type InP current blocking layer 6 appears on the surface. Further, since the n-type InP current confinement layer 7 remains except for the upper part of the mesa structure, the p-type InP current blocking layer 6 and the n-type InP current confinement layer 7 are different from the active layer of the mesa structure in the current confinement layer and the optical confinement layer. Work as a layer.

Next, as shown in FIG. 1E, the film thickness d = 1.
0 μm p-type InP over cladding layer 8, film thickness d =
A 0.4 μm p-type InGaAsP cap layer 9 is grown.

The device manufactured in this manner does not require a step of performing buried growth using a selective growth mask, and a buried structure laser device can be manufactured by a simple manufacturing process. Further, in the deposition of the n-type InP current confinement layer 7, it is not necessary to completely suppress growth on the mesa, so that high reproducibility and yield can be realized under a wide range of manufacturing conditions (mesa structure, growth condition).

(Embodiment 2) FIGS. 2 (a) to 2 (e)
FIG. 7 is a perspective view of a step for explaining another embodiment of the method for manufacturing the embedded structure semiconductor laser according to the present invention. As shown in FIG. 2A, a SiO ₂ film is deposited on the (100) plane n-type InP substrate 1 by a sputtering method, and a stripe width of about 2.5 μm is formed in the <011> direction by a photolithography technique. Si with selective growth region
The O ₂ growth mask 2 is formed.

Next, as shown in FIG. 2B, the film thickness d = 0.
6 μm Se-doped n-type InP buffer layer 3, film thickness d =
The undoped InGaAsP active layer 4 having a thickness of 0.1 μm and the p-type InP clad layer 5 having a thickness d = 0.3 μm are formed by MOV.
It grows by the PE method.

Next, as shown in FIG. 2C, after removing the SiO ₂ selective growth mask 2 by HF, the Zn-doped p-type InP current blocking layer 6 having a film thickness d = 0.8 μm is formed by MOVPE method. A Se-doped n-type InP current confinement layer 7 having a film thickness d = 1.0 μm is grown. At this time, n type I
The Se doping concentration of the nP current confinement layer 7 is set to 5 × 10.
^{When it is 18} cm ⁻³ or more, the growth of the n-type InP current confinement layer 7 on the n-type structure upper part above the mesa structure is suppressed, and the thickness is about 1/2 or less of the n-type InP current confinement layer 7 other than the mesa structure upper part. Only deposits.

Next, as shown in FIG. 2D, hydrogen chloride gas is flown into the reaction tube to etch the entire growth surface by about 0.5 μm. At this time, the growth of the n-type InP current confinement layer 7 is suppressed on the upper portion of the mesa structure, and the film thickness thereof is about 0.5 μm.
Below, the p-type InP current blocking layer 6 appears on the surface. Further, since the n-type InP current confinement layer 7 remains except for the upper part of the mesa structure, the p-type InP current blocking layer 6 and the n-type InP current confinement layer 7 are different from the active layer of the mesa structure in the current confinement layer and the optical confinement layer. Work as a layer.

Next, as shown in FIG. 2E, the film thickness d = 1.
0 μm p-type InP over cladding layer 8, film thickness d =
A 0.4 μm p-type InGaAsP cap layer 9 is grown.

The device manufactured in this manner does not require a step of performing buried growth using a selective growth mask, and a buried structure laser device can be manufactured by a simple manufacturing process. In addition, since it is not necessary to completely suppress growth on the mesa in depositing the n-type InP current confinement layer 7, high reproducibility and yield can be realized under a wide range of manufacturing conditions (mesa structure, growth condition).

(Embodiment 3) FIGS. 3 (a) to 3 (d) show
FIG. 9 is a perspective view of a step for explaining still another embodiment of the method for manufacturing the embedded structure semiconductor laser according to the present invention. In the figure, as shown in FIG. 3A, the (100) plane n-type In
A stripe width of about 2.0 μ is formed in the <011> direction on the P substrate 1 by photolithography and selective etching.
A mesa structure with a height of about 1.0 μm is formed.

Next, as shown in FIG. 3B, the Se-doped n-type InP buffer layer 3 having a film thickness d = 0.1 μm and the undoped InGa film having a film thickness d = 0.1 μm are formed by using the MOVPE method.
AsP active layer 4, p-type InP clad layer 5 with film thickness d = 0.8 μm, and Se-doped n-type I with film thickness d = 1.0 μm
The nP current confinement layer 7 is grown. At this time, n-type In
Se doping concentration of the P current confinement layer 7 is 5 × 10 ¹⁸ c
When m ⁻³ or more, the growth of the n-type InP current confinement layer 7 on the upper part of the mesa structure is suppressed, and the n-type I except the upper part of the mesa structure is formed.
Only a thickness less than about 1/2 of the nP current confinement layer 7 is deposited.

Next, as shown in FIG. 3C, hydrogen chloride gas is flown into the reaction tube to etch the entire growth surface by about 0.5 μm. At this time, the growth of the n-type InP current confinement layer 7 is suppressed on the upper portion of the mesa structure, and the film thickness thereof is about 0.5 μm.
Below, the p-type InP clad layer 5 appears on the surface. Further, since the n-type InP current confinement layer 7 remains except for the upper part of the mesa structure, the p-type InP clad layer 5 and the n-type InP current confinement layer 7 have a current confinement layer and an optical confinement layer with respect to the active layer of the mesa structure. Work as a layer.

Next, as shown in FIG. 3D, the film thickness d = 1.
0 μm p-type InP over cladding layer 8, film thickness d =
A 0.4 μm p-type InGaAsP cap layer 9 is grown.

The device manufactured in this manner does not require a step of performing buried growth using a selective growth mask, and a buried structure laser device can be manufactured by a simple manufacturing process. Further, in the deposition of the n-type InP current confinement layer 7, it is not necessary to completely suppress growth on the mesa, so that high reproducibility and yield can be realized under a wide range of manufacturing conditions (mesa structure, growth condition).

Although the n-type InP current confinement layer 7 was etched using chlorine gas in the above-described Examples 1 to 3, another etching gas was used or it was once taken out from the reaction tube. The same effect can be obtained by using the wet etching method.

Further, in the above-described Examples 1 to 3, it is apparent that the dopant used for the n-type InP current confinement layer 7 may be another group VI dopant such as Se.

In addition, in the first to third embodiments described above, the InP semiconductor laser has been described.
Other III-V group compound semiconductor lasers such as aAs system may be used.

[0034]

As described above, according to the present invention,
The buried structure semiconductor laser does not need a buried growth step using a selective growth mask, and can be manufactured by a simple manufacturing process. Also, complete deposition suppression on the mesas is not required for deposition of the n-type current confinement layer,
Laser devices can be manufactured in a wide range (mesa structure, growth conditions) and can be applied to various devices. Furthermore, since it is not easily affected by changes in growth conditions, high reproducibility and yield can be realized, and extremely excellent effects can be obtained.

[Brief description of drawings]

FIG. 1 is a sectional view of a step illustrating an embodiment of a method of manufacturing a buried structure semiconductor laser according to the present invention.

FIG. 2 is a cross-sectional view of a process illustrating another embodiment of the method for manufacturing a buried structure semiconductor laser according to the present invention.

FIG. 3 is a cross-sectional view of a process for explaining still another embodiment of the method for manufacturing a buried structure semiconductor laser according to the present invention.

FIG. 4 is a sectional view of a step for explaining still another embodiment of the conventional method for manufacturing a semiconductor laser with a buried structure.

FIG. 5 is a diagram showing the doping concentration dependence of the thickness of an n-type InP layer grown on a mesa.

[Explanation of symbols]

1 n-type InP substrate 2 SiO ₂ selective growth mask 3 Se-doped n-type InP buffer layer 4 undoped InGaAsP active layer 5 p-type InP clad layer 6 Zn-doped p-type InP current blocking layer 7 Se-doped n-type InP current confinement layer 8 p InP overclad layer 9 p-type InGaAsP cap layer

Claims (4)

[Claims] 1. A first step of forming a <011> direction mesa stripe having an active region on an n-type (100) III-V group compound semiconductor substrate, and a metal organic chemical vapor deposition method on the entire surface of the semiconductor substrate. And a second step of depositing a p-type semiconductor current blocking layer and an n-type semiconductor current confinement layer doped with a predetermined concentration of a group VI element, and etching the semiconductor substrate surface to form the p-type semiconductor current confinement layer only on the upper surface of the mesa stripe. A third step of processing so that a p-type semiconductor current blocking layer appears, and a fourth step of depositing a p-type semiconductor overclad layer and a p-type semiconductor cap layer on the p-type semiconductor current blocking layer and the n-type semiconductor current confinement layer The method of manufacturing a buried structure semiconductor laser, comprising: 2. The method according to claim 1, wherein the third step is
A method of manufacturing a buried structure semiconductor laser, wherein etching of the surface of the semiconductor substrate is performed in an organic metal vapor phase epitaxy apparatus using an etching gas. 3. A first method for forming a mesa stripe in the <011> direction on an n-type (100) III-V group compound semiconductor substrate.
And a second step of depositing an active layer, a p-type semiconductor current blocking layer, and an n-type semiconductor current confinement layer doped with a predetermined concentration of group VI element by metalorganic vapor phase epitaxy on the entire surface of the semiconductor substrate. A third step of etching the surface of the semiconductor substrate so that the p-type semiconductor current block layer appears only on the upper surface of the mesa stripe, and on the p-type semiconductor current block layer and the n-type semiconductor current block layer. And a fourth step of depositing a p-type semiconductor over-cladding layer and a p-type semiconductor cap layer on the substrate. 4. The method according to claim 3, wherein the third step is
A method of manufacturing a buried structure semiconductor laser, wherein etching of the surface of the semiconductor substrate is performed in an organic metal vapor phase epitaxy apparatus using an etching gas.