JPH05121722A - Semiconductor light emitting device and manufacture thereof - Google Patents

Abstract

PURPOSE:To flatten an element by a method wherein an abnormally grown part is removed by etching using the mask for selective growth used for formation of a current blocking layer, and the sectorially formed etched part is filled up by the insulating material such as polyimide and the like. CONSTITUTION:The active layer 11 on an N-type InP substrate 12 is InGaAsP semiconductor crystal corresponding to the luminous wavelength of 1.3mum, and the active layer 11 is sandwiched by a P-type InP clad layer 13 and an N-type InP buffer layer 12 from the upper and the lower sides in a mesa stripe 11. Both sides of the mesa stripe 111 are filled up by an Fe-doped InP current blocking layer 16, and a V-shaped groove filled up by polyimide 18 of insulator is provided on a part of the current blocking layer 16. An electrode layer 14, consisting of a P-type InGaAsP semiconductor layer, is formed on the P-type clad layer 13. Also, a P-type electrode 110 is formed on the upper surface of an element, and an N-type electrode 19 is formed on the reverse side of the substrate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high resistance layer embedded structure semiconductor laser which is important as a light source for optical transmission and a method for manufacturing the same.

[0002]

2. Description of the Related Art In order to improve the functionality and performance of a semiconductor light emitting device, an optical integrated device and an optical integrated circuit in which several devices are integrated on a substrate have been developed.

The semiconductor laser, which occupies a major part of the optical integrated device and the optical integrated circuit, has an embedded structure in order to reduce the oscillation threshold current and stabilize the transverse mode. That is, the mesa stripe is formed so that the active layer width is about 1 to 2 μm, and both sides thereof are filled with the current blocking layer. The crystal orientation in which the mesa stripes are arranged is important for forming the current blocking layer flat by burying growth.

In the (100) semiconductor substrate used for manufacturing the device, the (110) plane is used as the cavity surface of the semiconductor laser.

[0005]

[Outside 6]

There are two types available: a forward mesa stripe in which stripes are arranged in and a reverse mesa stripe in which stripes are arranged in the <110> direction. Both sides of the forward mesa stripe are Fe-doped I which is important as a current blocking layer, for example.
If the nP high resistance layer is to be embedded by the metalorganic vapor phase epitaxy method, which is easy to grow, abnormal growth as shown in FIG. 5 occurs and the current blocking layer cannot be formed flat.

Therefore, as a method for preventing such abnormal growth, conventionally, a method of providing an eaves on a mask for selective growth as shown in FIG. 6 (a) (Reference: Tatsuyuki Sanada et al. Applied Physics of Letters vol. 51 (1
987) 1054-1056), in the case of the forward mesa stripe, a void in which the current blocking layer does not grow is formed on the side surface of the mesa stripe as shown in FIG. 6B.
The entire element cannot be flattened. For this reason, the conventional mesa stripe is arranged only in the reverse mesa stripe direction in which the flattening of the current blocking layer is easy.

[0008]

However, when an optical integrated device or an optical integrated circuit is manufactured, the position where the semiconductor laser is arranged is always limited to the reverse mesa stripe direction for the above-mentioned reason. The degree of freedom in layout of integrated elements and integrated circuits in which the elements are arranged on the substrate is significantly narrowed. Therefore, it has been desired that the buried structure semiconductor laser can be manufactured not only in the reverse stripe direction but also in the forward mesa stripe direction.

An object of the present invention is to provide a semiconductor light emitting device having a high resistance layer embedded structure in which a resonator of a semiconductor laser is formed in a forward mesa stripe direction as a crystal orientation, and a manufacturing method thereof.

[0010]

To achieve the above object, a semiconductor light emitting device of the present invention comprises at least an active layer provided on a (100) plane of a semiconductor substrate having a first conductivity type. A clad layer having a second conductivity type provided on the active layer,

[0011]

[Outside 7]

A first mesa stripe region disposed along the first mesa stripe region, and on both sides of the first mesa stripe region,
A current blocking layer made of a semi-insulating high resistance semiconductor;
A groove having a V-shaped cross section, which is provided on both sides of the mesa stripe region and has at least a surface covered with an insulator. The groove between the V-shaped groove and the first mesa stripe region is It is characterized in that a current blocking layer is interposed.

In the semiconductor light emitting device of the present invention, at least the active layer provided on the (100) plane of the semiconductor substrate having the first conductivity type and the second conductivity type provided on the active layer. And a clad layer having

[0014]

[Outside 8]

A first mesa stripe region arranged along the first mesa stripe region, and both side parts of the first mesa stripe region,
A current blocking layer made of a semi-insulating high resistance semiconductor;
Under the mesa stripe region and the current blocking layer,
A second mesa stripe region that is arranged along the same direction as the first mesa stripe region and has a cross-sectional shape that spreads from the device upper surface toward the semiconductor substrate, and both sides of the second mesa stripe region. And an insulating layer embedded therein.

In the method for manufacturing a semiconductor light emitting device of the present invention, at least an active layer and a clad layer having a second conductivity type are sequentially laminated on the (100) plane of a semiconductor substrate having a first conductivity type. And a step of providing a mask having a predetermined shape on the laminated portion, and performing etching through the mask,

[0017]

[Outside 9]

Forming a first mesa stripe region disposed along the first mesa stripe region, burying a current blocking layer made of a semi-insulating high resistance semiconductor on both sides of the first mesa stripe region, Providing a mask having a shape exposing the first mesa stripe region and its peripheral portion;
A step of forming a V-shaped groove in a part of the current blocking layer by etching through the opening of the mask; and a step of flattening the entire device by embedding an insulator in the V-shaped groove. It is characterized by including.

Further, in the method for manufacturing a semiconductor light emitting device of the present invention, at least the active layer, the clad layer having the second conductivity type and the second conductivity are provided on the (100) plane of the semiconductor substrate having the first conductivity type. A step of sequentially laminating electrode layers having a mold, a step of providing a mask having a predetermined shape on the laminated portion, and etching through the mask,

[0020]

[Outside 10]

Forming a first mesa stripe region arranged along the line, and removing the mask;
Forming a current blocking layer made of a semi-insulating semiconductor on both sides and an upper portion of the first mesa stripe region to fill the first mesa stripe region; and an electrode layer having the second conductivity type and the electrode layer having the second conductivity type. By selectively etching the current blocking layer, a part of the current blocking layer is etched until at least the electrode layer is exposed, and a second mesa stripe region having a current blocking layer on a side of the first mesa stripe region is formed. And a step of planarizing the entire element by filling both sides of the second mesa stripe region with an insulator.

Further, in the method for manufacturing a semiconductor light emitting device of the present invention, a step of sequentially laminating at least an active layer and a clad layer having a second conductivity type on a (100) plane of a semiconductor substrate having a first conductivity type. And a step of providing a first mask having a predetermined shape on the laminated portion, and performing etching through the first mask,

[0023]

[Outside 11]

Forming a mesa stripe region arranged along the line, removing the mask, and forming a current blocking layer made of a semi-insulating semiconductor on both sides and an upper part of the mesa stripe region. The step of embedding the mesa stripe region, the step of providing a second mask that exposes the upper portion of the mesa stripe region and its peripheral portion, and the step of etching through at least the second mask to obtain the mesa stripe region. And a step of forming a groove along the extending direction of the mesa stripe region, and a step of flattening the entire element by embedding an insulator in the groove.

[0025]

In the present invention, the selective growth mask used when forming the current blocking layer is used as an etching mask,
The abnormal growth portion is removed by etching. At this time,
Since the stripes are arranged in the forward mesa stripe direction, the etching shape spreads toward the bottom, and the current blocking layer remains on the side surface of the active layer even after etching. The etched portion is filled with an insulating material such as polyimide to planarize the entire element. Alternatively, selective etching of the electrode layer and the current blocking layer arranged on the upper surface of the mesa stripe is used. That is, the mask for selective growth is not provided, the entire mesa stripe is filled with the current blocking layer, and only the current blocking layer is etched by selective etching. At this time, the electrode layer functions as an etching stopper layer, and the stripes are arranged in the forward mesa stripe direction.
The etching shape is a shape that spreads at the bottom with the electrode layer as the apex. Then, by embedding the etched portion with an insulator, the entire element can be planarized.

According to the present invention, a buried structure semiconductor laser having a resonator in the forward mesa stripe direction can be manufactured.

[0027]

Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1) FIG. 1 is a longitudinal sectional view showing the structure of an n-substrate Fe-doped InP embedded semiconductor laser as an embodiment of the semiconductor light emitting device of the present invention.

The active layer 11 is an InGaAsP semiconductor crystal having an emission wavelength of 1.3 μm. The active layer 11 is
The mesa stripe 111 on the n-type InP substrate 12 is sandwiched between the p-type InP clad layer 13 and the n-type InP buffer layer 12 from above and below.

The mesa stripe 111 is formed almost vertically, and both sides thereof are filled with the Fe-doped InP current blocking layer 16. A part of the current blocking layer 16 is provided with a V-shaped groove filled with an insulating polyimide layer 18, and the mesa stripe 111 is formed.
Fe-doped In between the active layer 1 and the polyimide 18
They are separated by the P current blocking layer 16.

The p-type electrode 1 is formed on the p-type clad layer 13.
P-type InGa so that good contact with 10 can be obtained.
An electrode layer 14 made of an AsP semiconductor layer is formed.
In addition, the Fe-doped InP current blocking layer 16 and the p-type electrode 11
A SiO ₂ film 17 is provided between 0 and the Fe-doped InP current blocking layer 16 and the polyimide 18.

The p-type electrode 110 is formed on the upper surface of the device, and the n-type electrode 19 is formed on the back surface of the substrate.

Next, a method of manufacturing the semiconductor laser shown in FIG. 1 will be described for each step with reference to FIGS.

First, on the (100) plane of the n-type InP substrate 15 (carrier concentration 1 × 10 ¹⁸ cm ⁻³ ), an n-type InP buffer layer containing Se as a dopant (carrier concentration 1 × 1
0 ¹⁸ cm ⁻³ , thickness about 1.0 μm) 12, and emission wavelength 1.
A non-doped InGaAsP active layer (thickness: approximately 0.1 μm) 11 corresponding to 3 μm, a p-type InP clad layer (carrier concentration: 5 × 10 ¹⁷ cm ⁻³ , thickness: approximately 0.2 μm) 13 having Zn as a dopant, and In with Zn as a dopant
After sequentially depositing an electrode layer 15 made of GaAsP (carrier concentration 5 × 10 ¹⁸ cm ⁻³ , thickness about 0.5 μm),
Mask of a predetermined shape made of SiO ₂ film (thickness of about 0.1
.mu.m, width about 1.5 .mu.m) 112 is formed ((a) of FIG. 2).

Next, dry etching is performed using the mask 112 to form a mesa stripe (width: about 1.5 μm, height: about 3.0 μm) 111 in which the stripe shape is substantially vertical.

[0036]

[Outside 12]

(FIG. 2B).

Using the mask 112 as a mask for selective growth,
A current blocking layer 16 made of an Fe-doped InP semiconductor having a thickness of about 3 μm is formed by selective growth. At this time, an abnormal growth portion 113 is generated in the vicinity of the mask for selective growth ((c) of FIG. 2).

A part of the surface of the current blocking layer 16 is covered with a resist mask 114 to form an element surface 115 which is not covered with the resist mask ((d) of FIG. 2).

Using the selective growth mask 112 and the resist mask 114 as selective etching masks, the abnormal growth portion 1
13 and a part of the current element layer 16 are removed by hydrochloric acid-based wet etching. At this time, the mesa stripe 11
Since No. 1 is arranged in the forward mesa stripe direction, the etching shape is a V-shaped groove 116. For this reason,
The side surface of the mesa stripe 111 is covered with the Fe-doped InP current blocking layer 16 ((e) in FIG. 2).

A SiO ₂ film (having a thickness of about 0.
1 μm) 17 is formed ((f) in FIG. 2), and the V groove 116 portion is filled with polyimide 18 to planarize the entire device ((g) in FIG. 2).

Finally, the SiO ₂ film on the electrode layer is removed,
After the electrode was formed, it was cut into individual chips to obtain a semiconductor laser having the structure shown in FIG.

The characteristics of the manufactured semiconductor laser at room temperature were an oscillation threshold current of 20 mA, an external differential quantum efficiency of 0.20 mW / mA, and a maximum output of 20 mW.

In this embodiment, the V-shaped groove formed by etching is filled with polyimide to flatten the entire device. On the other hand, as shown in FIG. 8, it was possible to obtain the device characteristics equivalent to those of this example even if only the SiO ₂ film was used without using polyimide.

Further, in this example, a mask made of a SiO ₂ film was used as a mask for selective growth when the Fe-doped InP current element layer was formed. On the other hand, Fe-doped In is formed on the entire surface of the mesa stripe without using a selective growth mask.
By forming a P current blocking layer (FIG. 7A) and using the resist mask of a predetermined shape and the electrode layer arranged above the mesa stripe as a selective etching mask (FIG. 7B), Even if the current blocking layer is etched ((c) of FIG. 7), the same element structure as that of this embodiment can be obtained.

(Embodiment 2) FIG. 3 is a longitudinal sectional view showing the structure of an n-substrate Fe-doped InP buried structure semiconductor laser as another embodiment of the semiconductor light emitting device of the present invention.

The active layer 11 is an InGaAsP semiconductor crystal having an emission wavelength of 1.3 μm. The active layer 11 is
The mesa stripe 111 on the n-type InP substrate 15 is sandwiched between the p-type InP clad layer 13 and the n-type InP buffer layer 12 from above and below.

The mesa stripe 111 is formed substantially vertically, and the Fe-doped InP current blocking layer 16 is arranged on both sides thereof. The mesa stripe 111 and the current blocking layer 16 form a second mesa stripe 117, and the second mesa stripe 117 has a skirt extending from the upper surface of the element toward the substrate. A SiO ₂ film 17 is formed on the side surface of the second mesa stripe 117, and both sides of the SiO ₂ film 17 are filled with a polyimide 18 which is an insulator to flatten the entire element.

The p-type electrode 1 is formed on the p-type cladding layer 13.
P-type InGa so that good contact with 10 can be obtained.
An electrode layer 14 made of AsP semiconductor is formed.

The p-type electrode 110 is formed on the upper surface of the device, and the n-type electrode 19 is formed on the back surface of the substrate.

Next, a method of manufacturing the semiconductor laser shown in FIG. 3 will be described for each step with reference to FIGS.

First, an n-type InP substrate (carrier concentration 1 ×
An n-type InP buffer layer with Se as a dopant (carrier concentration 1 × 1) is formed on the (100) plane 15 of 10 ¹⁸ cm ⁻³ ).
0 ¹⁸ cm ⁻³ , thickness about 1.0 μm) 12, and emission wavelength 1.
A non-doped InGaAsP active layer (thickness: about 0.1 μm) 11 corresponding to 3 μm, a p-type InP clad layer (carrier concentration: 5 × 10 ¹⁷ cm ⁻³ , thickness: about 2.0 μm) 13 having Zn as a dopant, and In with Zn as a dopant
After sequentially depositing an electrode layer 15 made of GaAsP (carrier concentration 5 × 10 ¹⁸ cm ⁻³ , thickness about 0.5 μm),
A mask with a predetermined shape made of SiO ₂ (thickness of about 0.1μ
m, width about 1.5 μm) 112 (FIG. 4A).

Next, dry etching is performed using the mask 112 to form a mesa stripe (width: about 1.5 μm, height: about 3.0 μm) 111 that is substantially perpendicular to the stripe shape.

[0054]

[Outside 13]

Then, it is formed ((b) of FIG. 4).

The mask 112 is removed, the current blocking layer 16 made of Fe-doped InP semiconductor is formed on the upper surface and the side surface of the mesa stripe, and the entire mesa stripe is embedded ((c) in FIG. 4).

Only the Fe-doped InP current blocking layer is etched by wet etching using a hydrochloric acid-based selective etching solution for the InP forming the current blocking layer and the InGaAsP layer forming the electrode layer. At this time, the electrode layer 14 serves as a mask for selective etching, and a second mesa stripe 117 having a height of about 5 μm and having an apex for the electrode is formed ((d) of FIG. 4).

A SiO ₂ film (with a thickness of about 0.1 is formed on the entire surface of the device).
.mu.m) (FIG. 4E), both sides of the second mesa stripe 117 are filled with polyimide 18 to planarize the entire device (FIG. 4F).

Finally, the SiO ₂ film on the electrode layer is removed,
After the electrode was formed, it was cut into individual chips to obtain a semiconductor laser having the structure shown in FIG.

The characteristics of the manufactured semiconductor laser at room temperature were an oscillation threshold current of 20 mA, an external differential quantum efficiency of 0.20 mW / mA, and a maximum output of 20 mW. The capacitance of the device was as small as 1 pF, and the cutoff frequency at which the modulation intensity decreased by 3 dB was 15 GHz.

In this embodiment, when the Fe-doped InP current blocking layer is formed, the electrode layer on the upper surface of the mesa stripe is
It was used as a mask for selective etching. On the contrary,
Even if the mask made of the SiO ₂ film is used as the mask for the selective growth and the selective etching for forming the current blocking layer as in the first embodiment, the same element structure as that of the present embodiment can be obtained. That is, by performing the selective etching in the state of FIG. 2C, and then removing the selective etching mask made of the SiO ₂ film, the state of FIG. 4D can be obtained.

[0062]

As described above, according to the present invention,
Without leaving abnormal growth or voids on the side of the mesa stripe,
The element can be planarized and manufactured, and a semi-insulating buried structure semiconductor laser having a resonator in the forward mesa stripe direction can be manufactured. As a result, when manufacturing an optical integrated device or an optical integrated circuit, the position where the semiconductor laser is arranged is not restricted to the conventional reverse mesa stripe direction,
The degree of freedom in the layout of arranging the individual elements on the substrate is remarkably expanded, and the optical integrated element and the optical integrated circuit can be made highly functional.

Further, according to the present invention, the electrode material formed on the upper surface of the device and the semi-insulating Fe-doped InP layer are separated by polyimide or the like, and the contact area between the two is made as small as possible. It is less likely that part of the electrode material will diffuse into the Fe-doped InP layer during the course of the process, impairing its quality.

Further, according to the present invention, by deeply etching the Fe-doped InP layer, the thickness of the burying layer made of polyimide can be increased, and the device capacitance can be further reduced.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view showing the structure of a semi-insulating high resistance layer-embedded structure semiconductor laser having a resonator in a forward mesa stripe direction, which is an embodiment of a semiconductor light emitting device of the present invention.

FIG. 2 is a vertical cross-sectional view of each step for explaining the method of manufacturing the semiconductor laser shown in FIG.

FIG. 3 is a vertical cross-sectional view showing the structure of a semi-insulating high resistance layer-embedded structure semiconductor laser having a resonator in the forward mesa stripe direction, which is another embodiment of the semiconductor light emitting device of the present invention.

FIG. 4 is a vertical cross-sectional view of each step for explaining the method of manufacturing the semiconductor laser shown in FIG.

FIG. 5 is a vertical cross-sectional view showing a configuration of a conventional semiconductor light emitting device in which both sides of a forward mesa stripe are embedded and grown.

FIG. 6 shows a structure of a conventional semiconductor light-emitting device in which a mesa stripe formed in the forward mesa stripe direction is buried and grown on both sides using a selective growth mask having an eaves, but the planarization of the entire element is not sufficient. FIG.

FIG. 7 is a vertical cross-sectional view showing a part of the manufacturing process for explaining the method for manufacturing the semiconductor light emitting device of the present invention which does not use the selective growth mask.

8 is a vertical cross-sectional view showing a device structure that does not use polyimide, as a modification of the semiconductor laser shown in FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 semiconductor substrate 2 mesa stripe 3 semiconductor burying layer 4 abnormal growth part 5 SiO ₂ mask 6 eaves provided on the mask 7 voids provided on the side surface of the mesa stripe 11 active layer 12 n-type InP buffer layer 13 p-type InP clad layer 14 p-type InGaAsP electrode layer 15 n-type InP semiconductor substrate 16 Fe-doped InP current blocking layer 17 SiO ₂ film 18 polyimide 19 n-type electrode 110 p-type electrode 111 mesa stripe 112 SiO ₂ mask 113 abnormal growth portion 114 resist mask 115 From resist mask Exposed element surface 116 Groove formed by etching 117 Second mesa stripe

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Koichi Wakita 1-1-6 Uchisaiwaicho, Chiyoda-ku, Tokyo Nihon Telegraph and Telephone Corporation

Claims (5)

[Claims] 1. An active layer provided on at least a (100) surface of a semiconductor substrate having a first conductivity type, and a clad layer having a second conductivity type provided on the active layer. [Outer 1] A first mesa stripe region disposed along the first mesa stripe region, a current blocking layer formed on both sides of the first mesa stripe region and made of a semi-insulating high-resistance semiconductor, and both side regions of the first mesa stripe region. A groove having a V-shaped cross section and having at least a surface covered with an insulator, the current blocking layer being interposed between the V-shaped groove and the first mesa stripe region. A semiconductor light-emitting device characterized in that 2. An active layer provided on at least the (100) plane of a semiconductor substrate having a first conductivity type, and a clad layer having a second conductivity type provided on the active layer, [Outside 2] A first mesa stripe region, a current blocking layer formed on both sides of the first mesa stripe and made of a semi-insulating high-resistance semiconductor, the first mesa stripe region and the current A second mesa stripe region disposed below the blocking layer along the same direction as the first mesa stripe region and having a cross-sectional shape that spreads from the upper surface of the element toward the semiconductor substrate. 2. A semiconductor light emitting device, comprising: an insulator layer embedded on both sides of the mesa stripe region of. 3. A semiconductor substrate having a first conductivity type (1
00) plane, at least an active layer and a clad layer having the second conductivity type are sequentially laminated, a mask having a predetermined shape is provided on the laminated portion, and etching is performed through the mask. By [outside 3] Forming a first mesa stripe region disposed along the first mesa stripe region, embedding a current blocking layer made of a semi-insulating high-resistance semiconductor on both sides of the first mesa stripe region, Providing a mask having a shape exposing the mesa stripe region and its peripheral portion; forming a V-shaped groove in a part of the current blocking layer by etching through an opening of the mask; And a step of flattening the entire element by burying an insulator in the mold groove. 4. A semiconductor substrate having the first conductivity type (1
00) plane, at least an active layer, a clad layer having a second conductivity type, and an electrode layer having a second conductivity type are sequentially laminated, and a mask having a predetermined shape is provided on the laminated portion. By etching through the mask, A first mesa stripe region disposed along the first mesa stripe region, a step of removing the mask, and a current blocking layer made of a semi-insulating semiconductor on both sides and an upper portion of the first mesa stripe region. Part of the current blocking layer until at least the electrode layer is exposed by the step of burying the first mesa stripe region and selectively etching the electrode layer having the second conductivity type and the current blocking layer. Etching to form a second mesa stripe region having a current blocking layer on the side of the first mesa stripe region, and filling both sides of the second mesa stripe region with an insulator to form the entire device. And a step of planarizing the semiconductor light emitting device. 5. A semiconductor substrate having a first conductivity type (1
00) plane, at least an active layer and a cladding layer having a second conductivity type are sequentially laminated, a step of providing a first mask having a predetermined shape on the laminated portion, and the first mask is By etching through Forming a mesa stripe region disposed along the mesa stripe region, removing the mask, and forming a current blocking layer made of a semi-insulating semiconductor on both sides and an upper portion of the mesa stripe region to form the mesa stripe region. And a step of providing a second mask that exposes a portion directly above the mesa stripe region and its peripheral portion, and etching both sides through at least the second mask, thereby forming both side portions of the mesa stripe region. And a step of forming a groove along the extending direction of the mesa stripe region, and a step of flattening the entire element by embedding an insulator in the groove, and a method of manufacturing a semiconductor light emitting device.