JP3249987B2 - Manufacturing method of buried semiconductor laser - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art Generally, 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 metal organic chemical vapor deposition, it is necessary to form a mesa stripe including an active region having a selective growth mask thereon and to bury a mesa stripe by selective growth. It gets complicated. In order to simplify the laser manufacturing process, a technique of embedding a mesa structure having an active layer without using a selective growth mask becomes important.

FIG. 4 is a perspective view of a process for explaining a semiconductor laser disclosed in, for example, Japanese Patent Application No. 3-285470 and a method of manufacturing the same. In FIG.
1A, an n-type InP buffer layer 3, an undoped InGaAsP active layer 4, and a p-type InP cladding layer 5 are grown on a (100) plane n-type InP substrate 1 by a metal organic chemical vapor deposition (MOVPE) method. I do.

Next, as shown in FIG. 4B, 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. 4C, a p-type InP current blocking layer 6 and a Se-doped n-type InP current confinement layer 7 are grown by MOVPE. At this time, the 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 mesa structure is completely suppressed, and the n-type InP layer 7 is not deposited on the mesa structure. The layer structure has the p-type InP layer 6 exposed on the surface. Since the n-type InP layer 7 remains except for the upper part of the mesa structure, the p-type InP layer 6 and the n-type InP layer 7 function as a current confinement layer and an optical confinement layer with respect to the active layer of the mesa structure.

Next, as shown in FIG. 4D, a p-type InP over cladding layer 8 and a p-type InGaAsP cap layer 9 are formed.
Grow.

With the device manufactured in this manner, a buried structure laser device can be manufactured by a simple manufacturing process since a process of performing burying growth using a selective growth mask is unnecessary.

[0008]

According to the method of manufacturing a buried semiconductor laser described above, the growth rate of an n-type semiconductor doped with a group VI dopant is reduced to a mesa based on the experimental results shown in FIGS. 5 (a) and 5 (b). The difference between the upper part of the structure and the place away from the mesa is used. However, if the mesa shape, dimensions, growth conditions, and the like change, the growth of the n-type semiconductor layer above the mesa structure cannot be completely suppressed (see FIG. 5). If an n-type semiconductor layer grows above the mesa structure (portion A in FIG. 4), the element 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 device structure due to the limitation of the mesa structure or the change of the growth condition, etc.
There is a problem that the yield decreases.

[0009] Therefore, the present invention has been made to solve the above-mentioned conventional problems, and its object 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 simple manufacturing process in a wide range (mesa structure, growth conditions). 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 the above object, a method of manufacturing a buried semiconductor laser according to the present invention comprises an active region having an active region on an n-type (100) III-V compound semiconductor substrate. A first step of forming a mesa stripe in the <> direction, and a p-type semiconductor current blocking layer over a whole surface of the semiconductor substrate by metalorganic vapor phase epitaxy.
A second step of depositing an n-type semiconductor current confinement layer doped with a group element, and a third step of etching the surface of the semiconductor substrate to process the p-type semiconductor current block layer only on the upper surface of the mesa stripe. And depositing a p-type semiconductor over cladding 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 semiconductor laser according to the present invention comprises a first step of forming a <011> direction mesa stripe on an n-type (100) III-V compound semiconductor substrate; 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 a group VI element on the entire surface of the substrate by metal organic chemical vapor deposition, and etching the surface of the semiconductor substrate A third step of processing so that the p-type semiconductor current blocking layer appears only on the upper surface of the mesa stripe;
-Type semiconductor current blocking layer and n-type semiconductor current confinement
And depositing a p-type semiconductor over-cladding layer and a p-type semiconductor cap layer on the layer.

Here, a method of manufacturing the above-mentioned buried semiconductor laser will be described as follows. In order to completely suppress the growth of the n-type layer on the mesa by the method described above, the allowable range of the mesa shape, dimensions, and growth conditions becomes narrow (for example, the mesa width W of about 1.1 μm shown in FIG. 5, the Se concentration). Is embedded with n-type InP of 8 × 10 ¹⁸ cm ⁻³ or more). However, even if the growth of the n-type layer cannot be completely suppressed, it is possible to realize a sufficient difference in film thickness between the n-formed long layer above the mesa structure and the n-formed long layer in other regions. 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, or 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 以下 or less,
A sufficient difference in film thickness from other regions can be realized. Therefore, after growing to the n-type layer, the entire surface is etched to remove only the n-type layer on the mesa and expose the p-type layer to the surface. Therefore, thereafter, by forming a p-type over cladding layer and a cap layer on the entire surface of the substrate, a structure in which the element resistance is small and a sufficient current block can be formed in portions other than the mesa region can be formed. Further, since the entire surface of the substrate is etched, the etching step does not require pretreatment such as patterning, and can be easily performed by etching using an etching gas in a reaction furnace.

[0013]

According to the method of manufacturing a buried structure semiconductor laser of the present invention, a buried structure semiconductor laser can be manufactured by a simple manufacturing process without a step of performing burying growth using a selective growth mask. Further, in the step of depositing the n-type semiconductor current confinement layer, high reproducibility and yield can be realized under a wide range of manufacturing conditions without completely suppressing the growth on the mesa.

[0014]

Embodiments of the present invention will be described below in detail with reference to the drawings. (Embodiment 1) FIGS. 1 (a) to 1 (e) are perspective views showing steps for explaining an embodiment of a method of manufacturing a buried semiconductor laser according to the present invention. In FIG. 1, as shown in FIG. 1A, a film thickness d = on a (100) plane n-type InP substrate 1 is formed.
A 1.0 μm Se-doped n-type InP buffer layer 3, an undoped InGaAsP active layer 4 with a thickness d = 0.1 μm, and a p-type InP cladding layer 5 with a d = 0.3 μm
It grows by 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 blocking 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 MOVPE. The current confinement layer 7 is grown. At this time, the n-type I
The Se doping concentration of the nP current confinement layer 7 is 5 × 10
^{When the} thickness is ¹⁸ cm ^-3 or more, the growth of the n-type InP current confinement layer 7 on the mesa structure is suppressed, and the thickness of the other n-type InP current confinement layer 7 is only about 以下 or less on the mesa structure. do not do.

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

Next, as shown in FIG. 1E, the film thickness d = 1.
0 μm p-type InP overcladding layer 8, 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 burying 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, since complete growth suppression on the mesa is not required, high reproducibility and yield can be realized under wide manufacturing conditions (mesa structure, growth conditions).

(Embodiment 2) FIGS. 2 (a) to 2 (e)
FIG. 11 is a perspective view of a step for explaining another embodiment of the method for manufacturing a buried semiconductor laser according to the present invention. As shown in FIG. 2A, an SiO ₂ film is deposited on the (100) plane n-type InP substrate 1 by a sputtering method, and has a stripe width of about 2.5 μm in the <011> direction by photolithography as shown in FIG. Si having selective growth region
An 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, thickness d =
The undoped InGaAsP active layer 4 having a thickness of 0.1 μm and the p-type InP cladding layer 5 having a thickness d = 0.3 μm are formed by MOV.
Grow by 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. A Se-doped n-type InP current confinement layer 7 having a thickness d = 1.0 μm is grown. At this time, the n-type I
The Se doping concentration of the nP current confinement layer 7 is 5 × 10
^{When the} thickness is ¹⁸ cm ^-3 or more, the growth of the n-type InP current confinement layer 7 on the n-type structure above the mesa structure is suppressed, and the thickness of the n-type InP current confinement layer 7 other than on the mesa structure is about 以下 or less of the thickness. Only accumulates.

Next, as shown in FIG. 2D, a hydrogen chloride gas is flowed into the reaction tube, and the entire growth surface is etched 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 thickness thereof is about 0.5 μm.
The p-type InP current blocking layer 6 appears on the surface. Since the n-type InP current confinement layer 7 remains except for the upper part of the mesa structure, the p-type InP current block layer 6 and the n-type InP current confinement layer 7 are different from the mesa structure active layer in the current confinement layer and the light confinement layer. Work as a layer.

Next, as shown in FIG. 2E, the film thickness d = 1.
0 μm p-type InP overcladding layer 8, 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 burying growth using a selective growth mask, and a buried structure laser device can be manufactured by a simple manufacturing process. Further, since it is not necessary to completely suppress the growth on the mesa in the deposition of 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 conditions).

(Embodiment 3) FIGS. 3 (a) to 3 (d)
FIG. 13 is a perspective view of a step for explaining still another embodiment of the method for manufacturing a buried structure semiconductor laser according to the present invention. In the same figure, as shown in FIG.
A stripe width of about 2.0 μm in the <011> direction is formed on the P substrate 1 by photolithography and selective etching.
A mesa structure having a height of about 1.0 μm is formed.

Next, as shown in FIG. 3B, a Se-doped n-type InP buffer layer 3 with a thickness d = 0.1 μm 3 and undoped InGa with a thickness d = 0.1 μm by MOVPE.
AsP active layer 4, p-type InP cladding layer 5 with d = 0.8 μm thickness and Se-doped n-type I with d = 1.0 μm thickness
The nP current confinement layer 7 is grown. At this time, the n-type In
Se doping concentration of P current confinement layer 7 5 × 10 ¹⁸ c
When it is set to m ⁻³ or more, the growth of the n-type InP current confinement layer 7 above the mesa structure is suppressed, and the n-type I
Only about half the thickness of the nP current confinement layer 7 is deposited.

Next, as shown in FIG. 3C, a hydrogen chloride gas is flowed into the reaction tube, and the entire growth surface is etched 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 thickness thereof is about 0.5 μm.
The p-type InP cladding layer 5 appears on the surface. Since the n-type InP current confinement layer 7 remains except for the upper part of the mesa structure, the p-type InP cladding layer 5 and the n-type InP current confinement layer 7 are different from the mesa structure active layer in the current confinement layer and the light confinement layer. Work as a layer.

Next, as shown in FIG. 3D, the film thickness d = 1.
0 μm p-type InP overcladding layer 8, 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 burying 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, since complete growth suppression on the mesa is not required, high reproducibility and yield can be realized under wide manufacturing conditions (mesa structure, growth conditions).

In the first to third embodiments described above, the n-type InP current confinement layer 7 was etched using chlorine gas. However, another etching gas was used, or the n-type InP current confinement layer 7 was once taken out of the reaction tube. The same effect can be obtained by using a wet etching method.

In the first to third embodiments described above, it is clear that the dopant used for the n-type InP current confinement layer 7 may be another group VI dopant such as Se.

In the first to third embodiments, an InP-based semiconductor laser has been described.
Other group III-V compound semiconductor lasers such as aAs type may be used.

[0034]

As described above, according to the present invention,
The buried structure semiconductor laser does not require a burying growth process using a selective growth mask, and can be manufactured by a simple manufacturing process. In addition, since it is not necessary to completely suppress the growth on the mesa in the deposition of the n-type current confinement layer,
A laser element can be manufactured in a wide range (mesa structure, growth conditions) and can be applied to various elements. Further, since it is hardly affected by changes in the growth conditions, extremely excellent effects such as high reproducibility and high yield can be obtained.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a process for explaining one embodiment of a method for manufacturing a buried semiconductor laser according to the present invention.

FIG. 2 is a cross-sectional view of a step for explaining 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 step for explaining still another embodiment of the method for manufacturing a buried semiconductor laser according to the present invention.

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

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]

REFERENCE SIGNS LIST 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 cladding layer 6 Zn-doped p-type InP current blocking layer 7 Se-doped n-type InP current confinement layer 8 p InP over cladding layer 9 p-type InGaAsP cap layer

Claims (4)

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