JP2917787B2 - Embedded semiconductor optical waveguide device and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a buried semiconductor optical waveguide device and a method of manufacturing the same.

[0002]

2. Description of the Related Art With the recent demand for higher capacity communication, low cost is indispensable for widely distributing an optical fiber communication system having potential high speed and large capacity to general subscribers. It is desired to realize optical semiconductor elements and optical integrated circuits. Conventionally, a method of etching a semiconductor layer has been used exclusively as a means for forming an optical waveguide device.However, variations in element characteristics due to non-uniform process in a substrate surface and a damage layer generated on the surface during dry etching have been used. This has been a problem in practical use of an optical integrated circuit that requires a large area and high uniformity, such as absorption loss.

As a new optical semiconductor device manufacturing technique for solving these problems, a growth inhibition mask is provided on a semiconductor substrate with a stripe-shaped opening interposed therebetween, and a metal organic chemical vapor deposition method is provided in the opening. (Hereinafter, referred to as MOVPE), a technique for partially epitaxially growing a semiconductor layer using MOVPE (hereinafter, referred to as MOVPE) has attracted attention. This technique can manufacture an optical waveguide element without etching a semiconductor layer, and is excellent in mass productivity such as simplification of a manufacturing process, and significant improvement in controllability and uniformity.

Further, the side surface of the selective growth layer is flattened on the order of an atomic layer, and the scattering loss of an optical signal can be ignored. Furthermore, it is also possible to partially change the bandgap energy within the same substrate plane with only one crystal growth, by skillfully applying the fact that the composition and thickness of the selective growth layer depend on the growth inhibition mask width. Therefore, it is ideally suited as a method of manufacturing an optical integrated circuit that requires monolithic optical functional elements having a plurality of different band gap energies. The inventors have already realized an integrated light source in which an electroabsorption optical modulator and a distributed feedback laser are monolithically integrated, a wavelength tunable DBR laser, and the like using this technology.

[0005] In addition to these light source devices, optical waveguide devices that perform guided light control by current injection are:
It is necessary to realize a current blocking function so that current can be efficiently injected into the optical waveguide layer (active layer). As one example, a buried structure is known in which the periphery of the active layer is filled with a cladding layer doped with a polarity opposite to that of the semiconductor substrate. This buried structure is extremely important from the viewpoint of device fabrication because it can reduce the waveguide width required for a single mode, and is widely used.

[0006]

The above-mentioned selective MOVPE
In the case where the active layer formed by the technique has a buried structure, buried growth is performed after partially or entirely removing the growth inhibition mask used for the selective MOVPE growth, but the impurity opposite to the polarity of the semiconductor substrate is suddenly removed. When the buried growth is heavily doped, the reverse breakdown voltage of the device is deteriorated, which causes the device to be deteriorated due to the leakage current, and significantly deteriorates the long-term reliability of the device. This is because the depletion layer width at the pn junction interface becomes thinner due to the high concentration of doping, and the effectively increased depletion layer electric field is applied to the buried regrowth interface having unstable crystallinity. This is due to a sudden increase in tunnel current. In general, even for photodetectors and electroabsorption optical modulators that always use a reverse bias without current injection, if the withstand voltage of the buried layer is insufficient for the actual use bias condition, the light absorption layer Since the voltage applied to the buried layer is clamped by the breakdown voltage of the buried layer, there arises a problem that required characteristics cannot be obtained.

In the case where the buried layer is heavily doped near the optical waveguide layer, the field distribution of the guided light spreads to this buried layer, so that excess loss due to impurity absorption here is not a small problem. Becomes further,
The active layer is usually undoped because of the necessity of performing current injection and electric field application, but the side surface of this active layer is exposed immediately before the burying growth, and in this state, the buried growth doped with a high concentration is performed immediately. Then, since impurities diffuse from the side toward the undoped active layer, there is a concern that the optical crystallinity and the reverse breakdown voltage may deteriorate.

In the present invention, in order to solve the above-mentioned problem which is a problem when fabricating a semiconductor optical waveguide device, a selective MOV is required.
The present invention proposes a method for manufacturing a buried-structured optical waveguide device having excellent compatibility with the PE growth technique.

[0009]

According to a method of manufacturing a semiconductor optical waveguide device having a buried structure according to the present invention, a pair of growth-inhibiting films opposed to each other with a stripe-shaped opening interposed therebetween is formed on a (100) semiconductor substrate [011]. Forming a light guide layer having a higher refractive index than the semiconductor substrate, transmitting light, emitting light, or absorbing light, and having a lower refractive index than the light guide layer and lowering the light guide layer from above and below. A step of epitaxially growing the sandwiched cladding layer in the opening using a selective metal organic chemical vapor deposition method, a step of partially or entirely removing the growth inhibiting film from the inside of the opening, the optical waveguide layer is the surface and not covered the sides of the cladding layer, as compared to the layer thickness of the cladding layer atop
The layer thickness on the side of the active layer and near the regrowth interface on the substrate
Thick, the impurity concentration is the 5 × 10 ¹⁶ cm ^-3 or less of the electric field relaxation layer, characterized in that it has at least a step of impurity concentration is epitaxially grown embedded and 5 × 10 ¹⁷ cm ^-3 or more embedded layer in this order .

In the method of manufacturing the buried-structured optical waveguide element, the width of the growth blocking film is partially different depending on the position of the stripe-shaped opening in the longitudinal axis direction.

[0011]

In the present invention, as a problem inherent in the buried structure optical waveguide device, attention is paid to the fact that the electric field strength of the depletion layer at the pn junction interface between the buried growth layer and the semiconductor substrate controls the reverse leakage current. The present invention proposes a layer structure for effectively reducing the electric field strength of the depletion layer to improve the reverse breakdown voltage. To reduce the electric field strength, the effective depletion layer width may be increased, and an electric field relaxation layer having an appropriate thickness with an impurity concentration reduced by about one digit or more with respect to the buried layer and the semiconductor substrate is provided between them. I just need to pinch it. As a method of sandwiching the electric field relaxation layer, a method of growing the electric field relaxation layer prior to the buried layer at the time of burying growth and a method of forming the electric field relaxation layer on the semiconductor substrate side in advance are conceivable.

In particular, the former requires only one less growth than the latter, so that the manufacturing process can be simplified and the cost can be reduced. Further, the absorption loss received by the light field spreading around the optical waveguide layer is also improved by covering both side surfaces of the active layer with the electric field relaxation layer in which the absorption of impurities is suppressed. Further, an effect of preventing impurities diffused from the buried layer toward the undoped active layer during the buried growth can be expected.

FIG. 1 is a diagram for explaining the operation of the present invention. As shown in FIG. 1A, when burying an active layer formed by using selective MOVPE, a stable (111) B plane is naturally formed on the side surface thereof.
As shown in (b), the growth rate in the [311] direction at the foot of the active layer is remarkably increased and a large amount of the growth material is consumed. As a result, the thickness of the layer near the regrowth interface on the side surface of the active layer and on the substrate increases about three times. As a result, while maintaining the effect of the electric field relaxation layer on the side of the active layer and the regrowth interface on the substrate that affect the reverse breakdown voltage and optical characteristics, the cladding layer and the buried layer are conducted only by impurity diffusion near the top of the cladding layer. It becomes possible to do.

As described above, when the method of manufacturing a buried semiconductor optical waveguide device according to the present invention is used, the device can be simplified, the breakdown voltage of the buried regrowth interface can be improved, and the optical crystal can be diffused by diffusing impurities into the active layer. It is extremely advantageous also from the viewpoint of device reliability due to a synergistic effect such as suppression of deterioration of performance and improvement of optical waveguide characteristics by reduction of absorption loss around the optical waveguide layer. In addition, in the present invention, when forming the optical waveguide layer, there is no need for wet etching of the semiconductor layer, so the yield and uniformity are excellent. Since there is no surface damage layer seen in the dry etching of the semiconductor layer, there is no unnecessary absorption loss.・ Smooth optical waveguide side of atomic layer order is naturally formed during growth, so there is no scattering loss ・ Selection such as no reflection seen in optical waveguide connection part (butt joint) formed by repeating partial growth The combination of excellent features unique to MOVPE growth makes it possible to provide an ideal manufacturing technique for realizing an optical integrated circuit.

[0015]

【Example】

(Embodiment 1) Hereinafter, the present invention will be described in detail with reference to the drawings. FIGS. 2A to 2D are diagrams illustrating a method of manufacturing an integrated light source in which an electro-absorption optical modulator and a DFB laser according to a first embodiment of the present invention are monolithically integrated. The manufacturing method will be described in the order of steps.

First, as shown in FIG. 2A, a diffraction grating 10 having a period in the [011] direction of 240 nm and a depth of 30 nm is placed on an n-InP substrate 101 having a plane orientation of (100).
2 is partially formed, a portion where the diffraction grating 102 is provided is a DFB laser region 103 (length 400 μm), and a flat portion without the diffraction grating 102 is an optical modulator region 104 (length 200 μm). An SiO ₂ film is formed on this substrate by using a thermal CVD method, and a stripe-shaped opening 10 having a width of 2 μm is formed by photolithography and etching.
5 and the width on both sides thereof is 1 in the DFB laser region 103.
7 μm, 8 μm in the optical modulator region 104, and the opening 105
Are processed into a pair of growth inhibition masks 106 whose longitudinal axis directions are parallel to the [011] direction of the n-InP substrate 101. However, the width of the growth blocking mask 106 is 25 mm between the DFB laser region 103 and the optical modulator region 104.
It is changed in a tapered shape over μm. Further, a portion 15 μm from the end face on the side of the optical modulator region is a window region 107 without the stripe-shaped opening 105.

Next, as shown in FIG. 2B, an n-InGaAsP optical waveguide layer 108 (100 nm thick) having a wavelength composition of 1.15 μm is formed in the stripe-shaped opening 105 by using a reduced pressure MOVPE growth apparatus. , An n-InP spacer layer 109 (thickness 40 nm), a seven-period undoped quantum well layer 110 including an undoped InGaAsP barrier layer (thickness 10 nm) having a wavelength composition of 1.3 μm and an undoped InGaAs well layer (thickness 7 nm), Composition 1.15 μm
Undoped InGaAsP hole accelerating layer 111 (thickness: 40 nm), p-InP cladding layer 112 (thickness: 200 nm)
nm) is continuously grown by selective MOVPE. At this time, an undoped InGaAs well layer and a wavelength composition of 1.3 μm
The growth conditions are adjusted so that the undoped InGaAsP barrier layer of FIG. 1 is lattice-matched to the n-InP substrate 101 in the DFB laser region 103. Undoped quantum well layer 11
The bandgap wavelength of 1.5 is 1.55 μm in the DFB laser region 103, and 1.0 band in the optical modulator region 104.
48 μm.

Next, as shown in FIG. 2C, a stripe-shaped opening 105 of the growth blocking mask 106 has a width of 7 μm in the DFB laser region 103 and a width of 5 μm in the optical modulator region 104.
The width of the undoped InP electric field relaxation layer 113 is increased to μm by photolithography and etching.
(Thickness: 40 nm), p-InP buried layer 114 (thickness: 1.4 μm), p ⁺ -InGaAs contact layer 115
(Thickness 200 nm) is grown by selective MOVPE. In order to electrically separate the DFB laser region 103 and the optical modulator region 104, the p ⁺ -InGaAs contact layer 115 is removed over a length of 25 μm from the boundary between the two regions toward the optical modulator region to form an isolation region 116.

Next, as shown in FIG. 2D, an insulating film 117 (thickness: 0.3 μm) is formed on the entire surface, and the p ⁺ -InGaAs contact layer 115 remains on the top after the buried growth. An opening is provided in the insulating film only by the photolithography technique and the etching in the portion where the insulating film is formed. Ti / A
A u-electrode 118 is deposited, and electrode patterning is performed by photolithography and etching. n-InP
After polishing the substrate 101 to a thickness of 100 μm, a Ti / Au
The electrode 119 is deposited. Finally, a low-reflection film 120 is formed on the end face on the side of the optical modulator area and a high-reflection film 121 is formed on the end face on the side of the DFB laser area. Is the value of those selectively grown in the part).

In the integrated light source manufactured as described above, when current is injected into the DFB laser region 103, the integrated light source has a wavelength determined by the pitch of the diffraction grating 102 and the effective refractive index obtained from the sectional structure of this region. Oscillates in uniaxial mode. Further, in the optical modulator region 104, the band gap energy of the light absorption layer having the quantum well structure is set to 1.48 μm so that light absorption at this wavelength when there is no bias is practically suppressed. . When an electric field is applied to this light absorbing layer, the absorption coefficient for transmitted light increases due to the quantum confined Stark effect (QCSE), so that the layer operates as a light intensity modulator.

When a reverse voltage of 3 V is applied to the optical modulator region 104, the light absorption layer of the quantum well structure becomes 200 kV / c.
m, the absorption coefficient for the oscillation wavelength of 1.55 μm is 4300c by QCSE.
m ^-1 also increases. Since the light confinement coefficient in the well layer composed of all seven layers is 4%, if the element length is 200 μm, 15
An extinction ratio of dB is obtained. In addition, by sandwiching the undoped InP electric field relaxation layer 113 during the burying growth,
The reverse leakage current at the buried regrowth interface was suppressed, and a reverse withstand voltage of 10 V was obtained, which was about three times the actually used bias of 3 V in the optical modulator region 104.

This undoped InP electric field relaxation layer 113
Is the p-I formed by the first selective MOVPE growth.
The top of the nP cladding layer 112 and the p-InP buried layer 11
4 naturally grows and the electrical conduction between the two becomes insufficient.
Due to the growth mechanism of E, [3] at the foot of the selective growth layer
11], the growth material species supplied from the growth inhibition mask 105 side is consumed in large amounts as the growth rate increases, so that the layer thickness at the top of the p-InP cladding layer 112 is 1
5 nm, which is about 1/3 of the layer thickness at the bottom of the selective growth layer. With this layer thickness, a p-type impurity (Zn)
Undoped InP electric field relaxation layer 113
The p-InP cladding layer 112 and the p-InP
There is no practical problem with electrical conduction with the buried layer 114. On the other hand, the layer thickness on the side surface of the quantum well layer 110 increases to about 100 nm due to the above-described effect. Therefore, pI
The diffusion of impurities from the nP buried layer 114 is suppressed, and at the same time, the p-InP buried layer 11 having a large impurity absorption.
4 is further away from the light field, so that there is also an effect of loss reduction.

In the integrated light source as shown in this embodiment, when there is a reflection on the exit end face on the side of the optical modulator area, the reflected light reciprocates in the optical modulator area 104 and the reflected light enters the DFB laser area 103. Feedback will be given. This residual end face reflection dynamically changes through light intensity modulation, causing a phenomenon called wavelength chirping, in which the oscillation wavelength fluctuates slightly with the light intensity modulation, and the optical signal after long-distance transmission in the optical fiber. This causes waveform deterioration. In order to suppress the wavelength fluctuation to a level at which there is no problem in practical use, it is necessary to set the wavelength variation to about 0.
Although the end face reflectance of 1% or less is required, the reflectance of a low-reflection film generally used for manufacturing an optical device is about 1% on average due to the restriction on the performance of a film forming apparatus. It is extremely difficult to achieve the required extremely low reflectance.
As a method capable of realizing this extremely low reflectance even with a normal low reflection film, in this embodiment, a window region 107 in which the optical waveguide layer is interrupted over a length of 15 μm is provided on the end face on the optical modulator side.
Light that has reached the boundary with the window region 107 after passing through the optical modulator region 104 is not confined in the horizontal direction.
Propagates while spreading in a conical manner to reach the end face. Of the light reflected at this end face, only the component that is perpendicularly incident on the end face can be recombined with the light absorbing layer of the light modulator region 104. % Or less can be realized relatively easily.

The DFB laser region 103 has an oscillation wavelength of 1.5
Single axis mode oscillation was performed at 5 μm and a threshold current of 10 mA. Also, from the DFB laser region 103 to the optical modulator region 1
The coupling efficiency of light to the light-receiving element 04 was 100%, and an output light power of 10 mW was obtained from the end face on the side of the light modulator region. When a voltage of 3 V was applied to the optical modulator region 104, an extinction ratio of 15 dB was obtained. The resistance between the DFB laser region 103 and the optical modulator region 104 was 10 kΩ, and electrical separation that was practically acceptable was realized. Further, when transmission was performed for 80 km in the 2.5 Gb / s band by using the integrated light source according to the present embodiment, wavelength chirping was sufficiently suppressed, and good transmission characteristics without code errors could be realized. further,
In a current deterioration test under a high temperature environment exceeding 50 ° C, 5
Even after a lapse of 000 hours or more, the reverse breakdown voltage deterioration of each region was not observed, and the effect of improving the device reliability of the undoped InP electric field relaxation layer 113 was confirmed.

(Embodiment 2) FIGS. 3A to 3D show a wavelength tunable distributed Bragg reflection type (D) according to a second embodiment of the present invention.
It is a figure explaining a manufacturing method of (BR) laser. The manufacturing method will be described in the order of the manufacturing steps.

First, as shown in FIG. 3A, a diffraction grating 20 having a period in the [011] direction of 240 nm and a depth of 30 nm is placed on an n-InP substrate 201 having a plane orientation of (100).
2 is partially formed, and the portion provided with this diffraction grating is referred to as DB.
R region 203 (length 250 μm), diffraction grating 202
The phase control area 204 (length 150 μm) and the DBR
The active area 205 (400 μm long)
m). On this substrate, SiO 2 is formed by thermal CVD.
_Two films are formed, and a stripe-shaped opening 206 having a width of 2 μm is formed by photolithography and etching, and the width on both sides thereof is 12 μm in the DBR laser region 203.
m, 8 μm in the phase control region 204, 1 in the active region 205
A pair of growth inhibiting masks 207 having a thickness of 7 μm and having the longitudinal direction of the opening 206 parallel to the [011] direction of the n-InP substrate 201 is processed. However, the width of the growth blocking mask 207 is tapered over a length of 25 μm at the boundary between the regions.

Next, as shown in FIG. 3B, an n-InGaAsP optical waveguide layer 208 (100 nm thick) having a wavelength composition of 1.15 μm is formed in the stripe-shaped opening 206 by using a reduced pressure MOVPE growth apparatus. n-InP spacer layer 2
09 (40 nm thick), a seven-period undoped quantum well layer 210 composed of an undoped InGaAsP barrier layer (thickness: 10 nm) and a undoped InGaAs well layer (thickness: 7 nm) having a wavelength composition of 1.3 μm, and an undoped wavelength composition of 1.15 μm InGaAsP hole acceleration layer 211 (thickness 4
0 nm), p-InP cladding layer 212 (200 nm thick)
m) is continuously subjected to selective MOVPE growth. At this time, the growth conditions are adjusted so that the undoped InGaAs well layer and the undoped InGaAsP barrier layer having a wavelength composition of 1.3 μm are lattice-matched to the n-InP substrate 101 in the active region 205. The band gap wavelength of the undoped quantum well layer 210 depends on the DBR region 203 and the phase control region 20.
4, 1.51 μm each in the active region 205,
1.48 μm and 1.55 μm.

Next, as shown in FIG. 3C, the growth preventing mask 207 is etched away from the inside by 2 μm in width to widen the stripe-shaped opening 206, where the undoped InP spacer layer 213 (thickness) is formed. 40 nm), p-I
nP buried layer 214 (1.4 μm thick), p ⁺ -In
A GaAs contact layer 215 (200 nm thick) is grown by selective MOVPE. In order to perform electrical isolation between the regions, a portion equally spanning the boundary of each region has a length of 2
P ⁺ -InGaAs contact layer 21 over 5 μm
5 is removed to form a separation region 216.

Next, as shown in FIG. 3D, an insulating film 217 (thickness: 0.3 μm) is formed on the entire surface, and the p ⁺ -InGaAs contact layer 215 remains on the top after the buried growth. An opening is provided in the insulating film 217 only by the photolithography technique and the etching at the portion where the insulating film 217 is formed. T
An i / Au electrode 218 is deposited, and electrode patterning is performed by photolithography and etching. n-
After polishing the InP substrate 201 to a thickness of 100 μm,
/ Au electrode 219 is deposited. Finally, the low reflection film 220 is formed on the end face on the DBR region side, and the high reflection film 2 is formed on the end face on the active region side.
21 are formed (note that each layer thickness described in the present embodiment is a value of a layer selectively grown in the opening of the active region).

The wavelength tunable DBR thus manufactured
When a current is injected into the active region 205, the laser oscillates in a single axis mode at a wavelength determined by the effective refractive index determined from the pitch of the diffraction grating 202 and the sectional structure of the DBR region 203. When a current is injected into the DBR region 203, the oscillation wavelength discretely changes toward the short wave side while repeating the axial mode jump with the decrease in the refractive index due to the plasma dispersion effect. Furthermore, if the phase matching condition of light reciprocating in the resonator is adjusted by injecting current into the phase control region 204, oscillation can be performed even between discretely changed oscillation wavelengths. realizable.

In the wavelength tunable DBR laser according to the present embodiment, single axis mode oscillation was performed at an injection current of 15 mA into the active region 205, and a maximum optical output of 15 mW was obtained. DBR
By performing current injection of 50 mA into the region 203, a maximum wavelength variable width of 7 nm was obtained. Further, the phase control area 20
Simultaneous injection of current into 4 also realized a pseudo-continuous tuning characteristic of the oscillation wavelength. In addition, since it is necessary to control the guided light by current injection in each of the regions, the current blocking function of the buried layer is extremely important.
By employing the electric field relaxation layer 213, the reverse leakage current of the pn junction surface buried and regrown is suppressed, and improvement in long-term stability and reliability of device characteristics can be expected.

[0032]

As described above, in the method of manufacturing a buried-structure optical waveguide device according to the present invention, the reverse tunnel leakage passing through the regrowth interface between the buried layer and the semiconductor substrate by sandwiching the electric field relaxation layer therebetween. The current can be suppressed. From now on, optical waveguide devices such as semiconductor lasers, optical modulators, optical filters, semiconductor optical amplifiers, and optical receivers and monolithically integrated optical integrated circuits can be realized easily and with high uniformity and high yield. Improvements in optical characteristics and reliability can be expected.

[Brief description of the drawings]

FIGS. 1A and 1B are cross-sectional views of a buried semiconductor optical waveguide device for explaining the operation of a method of manufacturing a buried semiconductor optical waveguide device according to the present invention.

FIG. 2A shows a first embodiment D of the present invention.
FIG. 7B is a plan view illustrating a method for manufacturing an integrated light source in which the FB laser and the electroabsorption optical modulator are monolithically integrated, and FIG.
FIGS. 4A to 4D are cross-sectional views taken along the line AA ′ in FIG.

FIG. 3A is a plan view illustrating a structure of a tunable DBR laser according to a second embodiment of the present invention;
(B)-(d) is sectional drawing in BB 'in (a) explaining the manufacturing method of a wavelength tunable DBR laser in order of a process.

[Explanation of symbols]

101 n-InP substrate having a (100) plane orientation 102 diffraction grating 103 DFB laser region 104 optical modulator region 105 stripe-shaped opening having a width of 2 μm 106 growth inhibition mask 107 window region 108 n-InGaAsP having a wavelength composition of 1.15 μm Optical waveguide layer (thickness 100 nm) 109 n-InP spacer layer (thickness 40 nm) 110 Undoped InGaAs / InGaAsP quantum well layer (wavelength composition of barrier layer 1.3 μm) 111 Undoped InGaAs with wavelength composition 1.15 μm
sP hole acceleration layer (thickness: 40 nm) 112 p-InP cladding layer (thickness: 200 nm) 113 Undoped InP spacer layer (thickness: 40 nm) 114 p-InP buried layer (thickness: 1.4 μm) 115 p ⁺ -InGaAs contact layer (Thickness 200
116) Isolation region 117 Insulating film 118, 119 Ti / Au electrode 120 Low reflection film 121 High reflection film 201 n-InP substrate with (100) plane orientation 202 Diffraction grating 203 DBR region 204 Phase control region 205 Active region 206 Width 2 μm stripe-shaped opening 207 Growth inhibition mask 208 n-InGaAsP optical waveguide layer having a wavelength composition of 1.15 μm (thickness: 100 nm) 209 n-InP spacer layer (thickness: 40 nm) 210 Undoped InGaAs / InGaAsP quantum well layer (barrier) (Wavelength composition of layer 1.3 μm) 211 Undoped InGaAs with wavelength composition 1.15 μm
sP hole acceleration layer (40 nm thick) 212 p-InP cladding layer (200 nm thickness) 213 undoped InP spacer layer (40 nm thickness) 214 p-InP buried layer (1.4 μm thickness) 215 p ⁺ -InGaAs contact layer (Thickness 200
nm) 216 Isolation region 217 Insulating film 218, 219 Ti / Au electrode 220 Low reflection film 221 High reflection film

Claims (3)

(57) [Claims] 1. A method of manufacturing a buried semiconductor optical waveguide device, comprising: forming a pair of growth-inhibiting films opposed to each other across a stripe-shaped opening on a (100) semiconductor substrate;
Forming a light guide layer having a higher refractive index than the semiconductor substrate, transmitting light, emitting light, or absorbing light, and having a lower refractive index than the light guide layer and lowering the light guide layer from above and below. A step of epitaxially growing the sandwiched cladding layer in the opening using a selective metal organic chemical vapor deposition method, a step of partially or entirely removing the growth inhibiting film from the inside of the opening, the optical waveguide layer is the surface and not covered the side surface of the clad layer, before
Compared to the layer thickness on the top of the cladding layer,
An electric field relaxation layer having a thicker layer near the regrowth interface on the plate and having an impurity concentration of 5 × 10 ¹⁶ cm ⁻³ or less;
At least a step of burying and epitaxially growing a buried layer of × 10 ¹⁷ cm ⁻³ or more in this order. 2. The method of manufacturing a buried-structure semiconductor optical waveguide device according to claim 1, wherein the width of the growth blocking film partially varies depending on the position of the stripe-shaped opening in the longitudinal axis direction. 3. An optical waveguide layer having a higher refractive index than the semiconductor substrate and propagating, emitting, or absorbing light on the (100) semiconductor substrate, and an optical waveguide layer having a lower refractive index than the optical waveguide layer and having a lower refractive index. A cladding layer sandwiched from above and below, and a buried layer covering the side surfaces of the optical waveguide layer and the cladding layer with a conductivity type different from that of the semiconductor substrate, wherein the optical waveguide layer and the cladding layer are [0]
11] formed in the direction of the mesa stripe, and the buried structure semiconductor optical waveguide element is a side (111) plane, have covered the sides of the optical waveguide layer and the cladding layer, wherein
Active layer side and substrate compared to layer thickness on top of cladding layer
The layer thickness near the upper regrowth interface is thicker, and the impurity concentration is 5
× 10 ¹⁶ cm ^-3 or less electric field relaxation layer and, buried structure semiconductor optical waveguide element impurity concentration formed on the electric field relaxation layer is characterized by having a 5 × 10 ¹⁷ cm ^-3 or more embedded layer .