JP3321800B2 - Design method of semiconductor optical integrated device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a semiconductor optical integrated device, and more particularly, to a selective MOVPE in the same chip.
(Metal-Organic Vapor Phase Epitaxy) The present invention relates to a design method for forming regions having different composition wavelengths, such as a light emitting portion and a passive waveguide portion, using growth.

[0002]

2. Description of the Related Art The selective MOVPE growth method is used when a compound semiconductor layer is formed between a pair of growth inhibition films, and the composition wavelength and the layer thickness within the same chip are changed by changing the width of each growth inhibition film. This is a means for controlling the thickness, and has an advantage that the manufacturing process of the optical integrated device can be greatly simplified.

FIG. 2 is a sectional view showing a state in which an active layer is grown by using a selective MOVPE growth method. Active layer 1
Is formed in the opening between the pair of growth stop films 10 by the selective MOVPE growth method. FIG. 2A shows a case where the width of the growth blocking film 10 is narrow, and the active layer 1 in the opening is formed.
Is not so different from the growth rate in a flat portion where there is no growth blocking film around. FIG. 2B shows the case where the width of the growth blocking film width 10 is large. In this case, the growth rate of the active layer 1 in the opening is sufficiently higher than the growth rate in other portions.

[0004] As described above, in the active layer 1, when the width of the growth-inhibiting film 10 is increased, the gas-phase density distribution near the opening where crystal growth is performed increases, and the growth rate increases. The growth rate of the active layer 1 mainly increases due to a change in the incorporation of the group III raw material, and increases in proportion to the width of the growth prevention film 10. In this case, the tensile strain increases with the growth rate,
The composition wavelength increases. Further, when the growing waveguide layer has a quantum well structure, in addition to the change in the composition wavelength of the material,
A wavelength change due to a quantum well width change is applied in the same direction. Thereby, in the same structure, a large wavelength composition change due to a change in the growth blocking film can be realized. The width of the growth blocking film can be easily changed by patterning the growth blocking film in the wafer plane, and the wavelength composition can be controlled in the same wafer plane which has been impossible in the past.

[0005] Japanese Patent Application Laid-Open No. 5-327111 describes a technique relating to a laser device and a method of manufacturing the same. FIG. 17 is a view illustrating the principle of the method for manufacturing a laser device described in the publication. In this method of manufacturing a laser device, a mask layer 22 made of silicon oxide or silicon nitride is formed on a semiconductor substrate 21 on which a cladding layer has been formed. Near the center of the mask layer 22, an active layer formation region 23 is formed.
Is formed so that the layer widths on both sides of the active layer forming region 23 are continuously increased in the X direction (laser oscillation direction).

As shown in FIG. 17B, the compound semiconductor layer deposited by the vapor phase epitaxial method using the mask layer 22 having the shape shown in FIG. 17A has a continuous film thickness in the X direction. Thicker. In the laser device formed by this manufacturing method, the forbidden band width of the active layer also changes continuously, so that the band of the gain characteristic is widened.

By this selective MOVPE technique, a spot size converter integrated laser (SSC-LD) in which a layer-thickness tapered waveguide is integrated in the same resonator, a distributed feedback type (DFB) Many semiconductor optical integrations such as a modulator integrated light source in which a semiconductor laser and an electroabsorption modulator are integrated, a distributed reflection semiconductor laser in which a distributed reflection passive waveguide capable of tunable operation and a semiconductor laser are integrated, and the like. The device can be easily manufactured.

[0008] As an example of device fabrication by the selective MOVPE growth method, the thickness of an optical waveguide is modulated in the optical axis direction using the same technique.
A method of manufacturing an SSC-LD for converting a light spot size is disclosed in Japanese Patent Application Laid-Open No. 6-165145. This structural diagram is shown in FIG. In this example, the active layer 1 and the tapered waveguide layer 2 are collectively formed by changing the pattern of the growth blocking film during the selective MOVPE. Further, the taper waveguide layer 2 is formed by changing the waveguide layer thickness and the composition wavelength in the optical axis direction by devising the pattern of the growth blocking film.
In this structure, about 4 dB is obtained as the coupling loss with the flat end optical fiber.

[0009]

In the case where the active layer and the tapered waveguide layer are formed at once by the selective MOVPE growth method, in order to realize good oscillation characteristics and coupling characteristics, the layer of the tapered waveguide layer is required. An optimal design of the thickness profile is required. In order to improve the oscillation characteristics, it is effective to sharpen the change in the layer thickness at the tapered waveguide layer introduction portion and reduce the absorption loss caused by the interband transition here. However, a steep change in layer thickness causes mode conversion loss, which not only degrades oscillation characteristics but also degrades coupling characteristics. For this reason, in order to realize an SSC-LD having excellent oscillation characteristics and coupling characteristics, precise control of the thickness profile of the tapered waveguide layer is essential.

[0010] As described above, in the selective MOVPE growth method, the composition wavelength and the layer thickness can be controlled relatively freely by changing the pattern of the growth-inhibiting film opposed to it along the longitudinal direction. However, in the selective MOVPE growth method, even if the growth stop film pattern is changed in steps, the composition wavelength and the layer thickness profile are about 100 μm due to the influence of gas phase diffusion.
It changes gradually over the range of m. FIG. 4 shows the results when the growth blocking film pattern of the SSC-LD was designed ignoring the effect of gas phase diffusion. The circles in the figure show the measurement results, and the solid lines show the estimation of the layer thickness profile in the case where the growth inhibition film pattern is designed ignoring the gas phase diffusion. In the figure, the estimated prediction and the measurement result coincide with each other only in a portion where the inclination of the passive waveguide portion having the tapered waveguide layer is gentle. However, in the vicinity of the boundary between the light emitting portion having the active layer and the passive waveguide portion having the tapered waveguide layer, which greatly affect the oscillation characteristics, the two are greatly different. It is clear from the figure that precise layer thickness control is not possible. Furthermore, in the actually measured layer thickness profile, the layer thickness profile near the boundary between the light emitting section and the passive waveguide section is gentle, which may cause an increase in absorption loss and a decrease in oscillation characteristics due to this. .

Therefore, in addition to the SSC-LD, in order to collectively form an optical integrated device having excellent oscillation characteristics by suppressing the deterioration of characteristics at the time of device integration by using the selective MOVPE growth method, a gap due to vapor phase diffusion during growth is required. The growth inhibition film pattern must be designed in consideration of the partial gas phase concentration distribution. Literature JO
URNALofAppliedPHYSICSVol.
According to P.78, p5373, in order to investigate the influence of gas phase diffusion, a two-dimensional diffusion equation had to be solved numerically, and much calculation time was required. In other words, it takes a lot of time to find a growth blocking film pattern that realizes the optimum layer thickness profile, which is not practical.

In order to solve the problems of the selective MOVPE growth method as described above, a structure for realizing an SSC-LD by forming an active layer and a core layer of a tapered waveguide by crystal growth in different steps is disclosed in the literature. ELECTRONIC SLETTERSV
ol. 31, No. 21, page 1838. Since the tapered waveguide formed with the same structure has a small absorption loss with respect to the laser oscillation wavelength, it has good oscillation characteristics such as a threshold current at room temperature of 5.6 mA, a slope efficiency of 0.41 W / A, and a maximum oscillation temperature of 135 ° C. Has been realized. Furthermore, by expanding the light spot size by integrating the tapered waveguide,
A good coupling characteristic with a coupling loss of 1.8 dB with the flat-end optical fiber is also realized. However, the structure is complicated, and there is a concern that sufficient reproducibility and uniformity of characteristics cannot be obtained when the device is put to practical use.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art, and it is an object of the present invention to improve the oscillation characteristics of an active layer and reduce the coupling loss of a tapered waveguide layer. The purpose is to design and accurately manufacture integrated devices.

[0014]

In order to achieve the above object, a method for designing a semiconductor optical integrated device according to the present invention is directed to a semiconductor optical integrated device which faces in the y direction with a striped opening extending in the x direction on xy coordinates. In a method of designing a semiconductor optical device manufactured by a selective MOVPE growth method in which a desired layer is grown in the opening by using a pair of growth stop films, R∞ is set to a growth rate sufficiently far from the growth stop film; local growth rates R _o, L _xdiff and L _Ydisff respectively x and y directions of the diffusion length, tau (x, y) as a raw material life, said x and y directions of the growth layer grown in the opening Rate R
_x (x) and R _y (y) are respectively represented by the following one-dimensional diffusion equation: (L _xdiff ) ² · τ (x) · {d ² R _x (x) / dx ² } = R _x (x) −R _o (x) _··· (Formula 1); and (L _ydiff ) ² · τ (y) · {d ² R _y (y) / dy ² } = R _y (y) −R∞ ··· It is characterized by using (Equation 2).

The method for designing a semiconductor optical integrated device according to the present invention comprises:
A semiconductor optical integrated circuit with a desired layer thickness profile can be manufactured by a calculation method that matches well with the actually measured value.

In the method of designing a semiconductor optical integrated device according to the present invention, the width of the opening in the y direction is limited, or
It is preferable to determine the growth rate in the direction from the experimental results. In this case, it can be manufactured more precisely with a desired layer thickness profile.

In the selective growth method according to the present invention, the light-emitting portion and the waveguide portion are formed in the opening by using a pair of growth inhibiting films opposed to each other in the y direction with a stripe-shaped opening extending in the x direction. Selective growth method for selectively growing a growth layer for
The growth blocking film has a first portion and a second portion sequentially arranged in the x direction corresponding to the light emitting portion and the waveguide portion to be formed, respectively, and the first portion has a substantially flat width. A flat region having a flat width region, a wide region having a width wider than the flat width region following the flat width region, and the second portion has a narrow region having a width smaller than the flat width region. And

[0018] According to selective growth of the present invention, the thickness z of the growth layers of the waveguide section to be formed, when the position x as a variable from the boundary portion between the light emitting portion, is formed on the curve of z = x ^8, It has been found that the thickness of the grown layer according to the eighth power curve gives particularly good characteristics.

The boundary between the flat width region and the wide region can be simply formed in a step shape, or the wide region can be formed in a step shape having a plurality of steps.

Further, instead of the above, the growth blocking film may be
A first portion and a second portion sequentially arranged in the x direction corresponding to the light emitting portion and the waveguide portion to be formed, wherein the first portion has a flat width region having a substantially flat width; Following the flat width region, there may be a widened region that increases in width toward the second portion, and the second portion may have a narrow width region in which the width decreases as the distance from the boundary with the first portion increases.

Here, assuming that the width of the flat width region is W as the dimension of the growth blocking film, the length of the widened region is 0.1 mm.
It is preferable that the width is 1 W to 10 W, the width is 1.2 W to 3 W, the length of the narrow region is 2 W to 20 W, and the width of the terminal is 0.1 W or less. More preferably, the width of the widened region is 0.3 W to 0.7 W and the width is 1.3 W to 1.7.
W, and the length of the narrow region is 7 W to 9 W. When a curved shape is adopted, a particularly good film thickness distribution of an eighth power curve is obtained, and a grown film having good characteristics is obtained.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Prior to a method of manufacturing a semiconductor optical device, a method of designing a layer thickness profile used in a selective MOVPE growth method of the present invention will be described.

In the present invention, the layer thickness profile during the selective MOVPE growth method is simply analyzed using the newly derived one-dimensional diffusion equation. Further, a selection M for iteratively calculating the derived one-dimensional diffusion equation to realize a desired layer thickness profile
Obtain a mask pattern for the OVPE growth method.

Reference JournalofAppliedP
physicsVol. According to pages 78 and 5373, the growth rate at each point on the wafer surface in the selected MOVPE can be obtained from the following two-dimensional diffusion equation. ｛∂ ² R (x, y) / ∂x ² ｝ + ｛∂ ² R (x, y) / ∂
y ² ｝ = {R (x, y) -R} / ｛(L _diff ) ² · τ
(X, y)｝ (1) where R (x,
y) is the growth rate on the substrate surface, R∞ is the growth rate sufficiently far from the growth stop film, L _diff is the diffusion length, τ (x,
y) represents the raw material life, respectively. Since Equation 1 is a two-dimensional partial differential equation, solving it numerically requires a lot of calculation time.

To simplify the calculation, the following assumptions are made:
Make Equation 1 more manageable. FIG. 5 shows the assumed coordinate system. First, a selective MOVPE growth region is assumed to be a narrow stripe of 2 μm or less, and the growth rate modulation in the y direction at the opening of the growth inhibition film 10 due to migration is ignored. Furthermore, if attention is paid only to the growth rate of the opening portion of the growth blocking film and the growth region outside the opposite oxide film is ignored, the two-dimensional diffusion equation is separated into two one-dimensional diffusion equations. X at the opening of the blocking film
A directional layer thickness profile can be determined. (L _xdiff ) ² · τ (x) · {d ² R _x (x) / dx ² } = R _x (x) −R _o (x) (2)

Here, L _xdiff is the diffusion length in the [011] direction in which the stripe is formed, R _x (x) is the growth rate in the x direction, and R _o (x) is the value when there is no gas phase diffusion. This shows the local growth rate determined by the width of the growth inhibiting film. On the other hand, the growth rate at the opening of the growth blocking film when the width Wm of the growth blocking film is changed can be obtained from the following diffusion equation. (L _ydiff ) ² · τ (y) · {d ² R _y (y) / dy ² } = R _y (y) −R} (Equation 3) where L _ydiff is in the y direction. Indicates the diffusion length. L _{ydiff in}
Indicates the diffusion length commonly used at the edge of the growth inhibiting film. On the other hand, L _{xdiff in} Equation 2 represents the [011] direction vapor phase diffusion length at the opening of the growth barrier film due to the vapor phase concentration distribution on the wafer, which is generated by the stripe-shaped growth inhibitory film for selective growth.
Therefore, the growth rate with respect to the width of the growth inhibition film at the opening of the growth inhibition film is obtained by using Expression 3, and this is substituted into Expression 2 as _Ro (x), whereby the film in the x direction at the opening of the growth inhibition film is obtained. A thickness profile can be determined.

However, in Equation 3, there is an insufficiency as an analytical model, for example, the raw material adsorption life on the growth inhibiting film is not infinite, and the experimental results cannot be explained unless a finite value is assumed. Therefore, in the present model, the growth rate with respect to Wm is determined by using the experimental result, and this is substituted for R _o (x) in Expression 2 to determine the film thickness profile in the x direction.

Equation 2 is a non-homogeneous linear differential equation.
From, the general solution can be obtained analytically. Only
Here, we need to deal with any pattern
For ease, solve Equation 2 numerically using the difference method.
And Assuming that the material life at the opening of the growth inhibition film is 1,
Then, when Expression 2 is differentiated, the following expression is obtained. For example, stop growth
If the film width Wm is in the range of 25 μm to 100 μm, Δx
By setting = 1 μm, a good approximation can be obtained. (R_xi-1)-(2 · R_xi) + (R_{xi + 1})-｛Δx · R_xi
/ (L_xdiff)^Two｝ =-｛Δx · R_oi/ (L_xdiff)^Two｝
... (Equation 4) As for the boundary condition, Wm is changing.
Where the gas phase concentration distribution is sufficiently far away from
In R_x(X) is the local growth rate R determined by Wm
_oIt was given by the following equation as being equal to (x). R_x0= R_o1..... (Equation 5) (R_{xk + 1}) = R_OK...
(Equation 6) Here, k indicates a grid number at an end point. boundary
Considering the conditions, the difference equation at the end point is as follows. R_x2− (2 · R_x1)-｛Δx · R_x1/ (L_xdiff)^Two｝ =-｛Δx · R_o1/ (L_{xd iff} )^Two｝ -R_o1..... (Equation 7) (R_xk-1)-(2 · R_xk)-｛Δx · R_xk/ (L_xdiff)^Two｝ =-｛Δx · R_OK/ (L_xdiff)^Two｝ -R_OK... (Equation 8) When (Equation 4) to (Equation 8) are collectively displayed as a matrix (Equation 9)
Get.

[0029]

(Equation 1)

Equation 10 is obtained by simplifying equation 9. E · R = R _o ····· (Equation 10) where E is the formula 9 the matrix on the left, R represents shows column vector of Formula 9 left, R _o is a column vector of Formula 9 right respectively. The growth rate at each point can be obtained by solving the simultaneous equations of Expression 11 as shown in the following expression. R = E ^-1 · R _o ····· (Equation 11) As described above, since the present model only solves a system of linear equations of several hundred elements, a major feature is that the calculation can be completed in a short time. .

Next, a method of back-calculating the growth inhibition film pattern for the selected MOVPE for realizing an arbitrary layer thickness profile by iterative calculation will be described. Growth stop layer pattern to achieve the optimum profile, as well as iterative equation 12 to fall within a certain range residuals between the target layer thickness profile P to give a layer thickness profile R _m and the initial value obtaining determined from Equation 2 It was obtained by calculating the film thickness profile sequentially using Equation 13. R _om = (R _om -1) + γ · (P−R _m−1 ) (Equation 12) R _m = E ⁻¹ (Y · R _om ) (Equation 13) Here, P is a longitudinal vector having a target film thickness profile as an element, and γ is a relaxation coefficient. Here, 0.333 is used so that iterative calculation can be easily converged. Also, the subscript m of the vector R and R _o indicates the number of iterations, a further Y is a matrix containing the boundary conditions shown in the following equation.

[0032]

(Equation 2)

In this way, by designing a growth inhibition film pattern to be used for selective MOVPE by iterative calculation of a one-dimensional diffusion equation, a desired layer thickness profile can be obtained by one trial production.

Hereinafter, a method for manufacturing a semiconductor optical integrated device according to an embodiment of the present invention will be described with reference to the drawings.

(Embodiment 1) In the analysis model of the present invention, the only parameter required for calculation is the diffusion length. Here, as shown in FIG. 5, a selective MOVPE growth method is performed using a growth-blocking film pattern in which the vicinity of the boundary between the light-emitting portion and the passive waveguide portion is changed in a step-like manner. The diffusion length was determined by fitting the result to the diffusion length. As a result, the growth pressure is 75 to
35 μm for rr under reduced pressure growth and 20 μm for normal pressure growth
m. FIG. 6 shows a comparison between the calculation result of the layer thickness profile by the one-dimensional diffusion equation shown in the present embodiment and the measurement result. In the selective MOVPE growth method, the growth inhibition film pattern shown in FIG. The calculation results and the experimental results agree very well in both the reduced pressure growth and the normal pressure growth, and it is understood that the analysis model according to the present embodiment can accurately predict the layer thickness profile for the growth inhibition film pattern. h (x) = h ₂ + (h ₁ −h ₂ ) · [1- {x / (L _ssc )}] ⁸ (15)

(Embodiment 2) FIG. 7 is a sectional view of an SSC-LD manufactured according to a second embodiment of the present invention. The thickness profile of the tapered waveguide layer is expressed by the following equation:
The growth inhibition film pattern used in the selective MOVPE growth method was determined as shown in FIG.

Equation 15 is theoretically introduced to realize a desired layer thickness profile, where h ₁ is the layer thickness of the active layer, h ₂ is the layer thickness at the exit end of the tapered waveguide layer, and L _ssc indicates the region length of the layer thickness tapered waveguide. FIG. 8 shows the desired layer thickness profile. The target layer thickness profile is flat in the light emitting portion and has no variation in film thickness, and the layer thickness is sharply reduced in the introduction portion of the passive waveguide portion having the tapered waveguide. As a result, the composition wavelength change at the tapered waveguide introduction part is increased, and the absorption loss at that part is reduced.

FIG. 1B shows a state in which a growth inhibition film pattern used for the selective MOVPE growth method for realizing an eight-thick layer thickness profile is obtained by iterative calculation of the one-dimensional diffusion equation shown in the present invention. The feature of the growth blocking film pattern obtained by the 20 repetitive calculations is that the growth blocking film width increases in a delta function at the boundary between the active layer 1 and the tapered waveguide layer 2. Thereby, a steep change in the layer thickness at the tapered waveguide introduction portion is realized. FIG. 9 shows a comparison between the layer thickness profile obtained from the growth-blocking film pattern by the iterative calculation of the one-dimensional diffusion equation of the present invention and the calculation result of the power-of-eight profile of equation (15). The two values agree very well, and it is understood that the design method according to the present embodiment is extremely effective for mask design by the selective MOVPE growth method. In addition, in the layer thickness profile obtained this time, since the change in the layer thickness in the active layer and the change in the composition wavelength due to the change in the layer do not occur in the conventional growth-blocking film pattern, the oscillation characteristics can be improved. . Due to the integration of the tapered waveguide, the thickness of the waveguide at the emission end is reduced to 1/3 of that of the active layer, the light spot size is increased here, the aspect ratio is improved, Direct coupling characteristics with a one-mode optical fiber can be realized.

The manufacturing method according to the second embodiment of the present invention is represented by SS
A description will be given along the manufacturing process of the C-LD with reference to FIGS. First, on the (001) plane of the n-InP substrate,
A growth inhibition film 10 made of a 100 nm thick SiO2 film is deposited by a thermal CVD method. Subsequently, a resist pattern used for selective MOVPE is formed by a photolithography process. The growth stopper film 10 is etched using the diluted hydrofluoric acid to complete a substrate used for growth. FIG. 10 shows the SSC-LD manufactured by the steps up to here. Selection M
For the OVPE, the growth blocking film pattern shown in FIG.
The first SCH layer made of InGaAsP having an m wavelength composition is 60 nm, the MQW (multiple quantum well) layer is 60 nm, and the second SCH layer made of InGaAsP having a 1.13 μm wavelength composition is 60 n.
The m and p-InP cladding layers are epitaxially grown in order of 100 nm. In this manufacturing method, in addition to the active layer, a tapered waveguide layer is formed at a time by selective MOVPE. MQW
The layers are seven well layers composed of 1.4 μm wavelength InGaAs and a 1.13 μm wavelength InGa sandwiched between the well layers.
The active layer 1 was designed so that the thickness of the well layer was 7 nm, the thickness of the barrier layer was 15 nm, and the oscillation wavelength was 1.3 μm.

Here, the pattern of the growth inhibiting film which gives a particularly good film thickness profile shown in FIG. 1A will be described in detail. FIG. 18 is an enlarged view of this growth blocking film pattern. The pair of growth blocking films 10 are arranged symmetrically with the opening interposed therebetween. When the width in the flat width region of the light emitting portion having a flat width is W, a preferable dimension of each portion of the growth blocking film 10 is as follows. The length L12 from the end of the flat region to the boundary between the light emitting unit and the waveguide is in the range of 0.1 W to 10 W, and the width W1 of the boundary is in the range of 1.2 W to 3 W. The preferred length L23 from the boundary to the end of the waveguide is in the range of 2W to 10W. The width W2 at the end of the waveguide is 0.2 W or less.

As the dimensions of the growth inhibiting film having a more preferable shape, L12 is 0.3 W to 0.7 W, and W1 is 1.3 W to 1.3 W.
1.7 W, and L23 is 7 W to 9 W.

FIG. 15 shows the measurement results of the layer thickness profile formed of the growth inhibition film by this pattern design, and the expression 1
5 is a graph showing a comparison with a calculation result of a layer thickness profile that becomes an eighth power distribution using No. 5; The circles indicate the measurement results, and the solid line indicates the target layer thickness profile represented by Expression 15. Both agree very well, and it can be seen that the layer thickness profile can be controlled with high accuracy by using this design method.

The growth layer does not grow on the growth blocking film but grows selectively on the n-InP substrate 8 in the gap.
After the active layer 1 and the tapered waveguide 2 are formed at once, the growth blocking film 10 made of a SiO2 film is removed using hydrofluoric acid. This is shown in FIG. After the formation of the waveguide, a growth inhibition film 10 of a SiO2 film is deposited again on the entire surface. After that, the other growth blocking films 10 are removed by hydrofluoric acid by a self-alignment process so that the growth blocking films 10 are formed only on the tops of the waveguides directly formed. This is shown in FIG. MOVPE is again performed using this growth stop film 10 as a mask.
After the growth, the p-InP current blocking layer 3 was set to 0.7 μm.
The m and n-InP current blocking layers 4 are formed in order of 0.7 μm. This is shown in FIG.

Next, after removing the growth inhibiting film 10, the p-I
An nP cladding layer 5 is formed. p-InP cladding layer 5
Is made thicker than a normal LD structure to 5 μm so that a part of the light field does not reach the electrode due to the enlargement of the spot size. After the growth of the p-InP cladding layer 5, pI
The nGaAs contact layer 6 is grown to have a structure that allows easy ohmic contact with the electrode. This is shown in FIG. Subsequently, an SiO2 film is formed on the entire surface, and the SiO2 film is patterned by a photolithography process, and an opening is formed so that a current flows only in the active layer 1. TiA on both sides
After forming the p-electrode 7 and the n-electrode 9 made of u, an electrode alloy is formed at 430 ° C. to complete the device.

The device was cut out from the wafer with the length of the light emitting portion being 300 μm and the length of the passive waveguide portion being 200 μm.
The properties were evaluated. When a high reflection coating of 95% was applied to the end face of the light emitting portion, the threshold current at room temperature was 4%.
As a result, a good oscillation characteristic of 14 mA was realized even at 85 ° C. Conventionally, the external differential quantum efficiency of 0.38 W / A was better at 0.5 ° C. and 0.45 W / A at 25 ° C. and 85 ° C., respectively. The horizontal and vertical radiation angles of the element are 10 degrees and 1
A narrow value was realized once. This is about 1/3 of the radiation angle of 30 ° obtained by a normal LD. As a result, the coupling loss with the 1.3 μm zero-dispersion fiber which is usually used is 1.5 dB instead of the conventional 3.5 dB.
And became better. The characteristic temperature representing the temperature dependence of the oscillation threshold current has been 40K in the past, but has now been increased to 60K.
And improved.

Further, the position tolerance at which the coupling loss increases by 1 dB is 1.8 μm, and a good coupling characteristic which can sufficiently be applied to passive alignment, which is an inexpensive mounting method, is also realized. Conventionally, coupling loss obtained by a semiconductor laser having a normal structure having a large mode mismatch with an optical fiber is 10 d.
Considering that B is 8.5, in the present embodiment example, 8.5.
Improvement in the coupling characteristics of dB can be realized by integration of the tapered waveguide.

(Embodiment 3) In Embodiment 2, a method of manufacturing a device using a growth-blocking film pattern obtained by iterative calculation has been described. However, in actual device fabrication, it may be difficult to form a pattern in which the growth blocking film width increases in a delta function at the boundary between the active layer and the tapered waveguide layer used in the second embodiment. In that case, it is possible to approximate the increase in the delta-function growth blocking film width with a rectangle. FIG. 16 shows a calculation result when the growth blocking film width at the boundary between the active layer and the tapered waveguide layer is sharply increased from 25 μm to 35 μm. In the figure, W indicates a growth inhibition film width of 25.
The width increases from μm to 35 μm. W is 22μ
It can be seen that by setting m, the distribution becomes almost equal to the eighth power distribution of the optimum layer thickness profile. By further changing W, L
It can be seen that the layer thickness flatness at the portion D can be controlled. An SSC-LD can be manufactured by the same manufacturing procedure as in Embodiment 2 of the present invention using the growth blocking film pattern shown in FIG.

In the method of designing a semiconductor optical integrated device according to the above-described embodiment, the designed growth prevention film pattern may be provided with a projection shape having a step shape instead of one projection shape. In this case, the same effect can be obtained.

(Other Embodiments) In the above example, the Fabry-Perot structure is used. However, a passive waveguide is provided between the LD portion and the tapered waveguide, and a DBR for forming a diffraction grating is provided here.
A laser structure may be used. Further, a DFB laser structure in which a diffraction grating is formed in the LD section may be used. D on the same substrate
An FB laser and a modulator may be formed, and a growth blocking film pattern may be designed by the same design method as described in the present embodiment, to form a modulator integrated light source. Further, in the above-described embodiment, the MQW is made of the InGaAsP / InP-based material, but the AlGaAs / GaAs-based material, the AlGaInP / GaInP-based material, and the ZnSe are used.
GaN-based or other compound semiconductor materials may be used.

The present invention has been described based on the preferred embodiment. However, the method of designing a semiconductor optical integrated device of the present invention is not limited to the configuration of the above-described embodiment, and is not limited to the above embodiment. A method of designing a semiconductor optical integrated device in which various modifications and changes have been made from the configuration of the embodiment is also included in the scope of the present invention.

[0051]

As described above, in the method of designing a semiconductor optical integrated device according to the present invention, the growth inhibition film pattern used for the selective MOVPE growth method is designed by using a one-dimensional diffusion equation, so that a precise taper guide can be obtained. It is possible to provide a design method capable of controlling the wave path shape and realizing an SSC-LD having good oscillation characteristics.

Further, the present method can be used not only for SSC-LD but also for mask design of an optical integrated device manufactured by using a selective MOVPE growth method such as a modulator integrated light source, a variable wavelength light source, and a wavelength selective light source. In this case, the characteristics can be prevented from deteriorating during element integration, and the characteristics can be greatly improved.

Further, the present invention is very important not only for reducing the price of an optical module but also for reducing the price of a subscriber optical communication system.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a growth blocking film pattern used in a second embodiment of the present invention and a graph showing calculation results.

FIG. 2 is a cross-sectional view showing a state in which an active layer is grown due to a change in a growth blocking film width in a selective MOVPE growth method.

FIG. 3 shows an SSC described in JP-A-6-165145.
It is a structural diagram of -LD.

FIG. 4 is a comparison between a design example of a layer thickness profile according to the related art and measurement results.

FIG. 5 is a coordinate system assumed in the present invention.

FIG. 6 is a graph showing a comparison between a calculation result and a measurement result of a layer thickness profile used in the first embodiment of the present invention.

FIG. 7 shows an S manufactured according to the second embodiment of the present invention.
It is sectional drawing of SC-LD.

FIG. 8 is a graph showing a target layer thickness profile of the second embodiment of the present invention.

FIG. 9 is a graph comparing a measurement result of a layer thickness profile obtained from a growth inhibition film pattern by an iterative calculation of a one-dimensional diffusion equation of the present invention with a calculation result of a power-of-eight profile of Equation (15).

FIG. 10 is a structural diagram of the SSC-LD manufactured in the first stage of the manufacturing process according to the embodiment.

FIG. 11 is a structural diagram of an SSC-LD manufactured in a second stage of the manufacturing process according to the embodiment.

FIG. 12 is a structural diagram of an SSC-LD manufactured in a third stage of the manufacturing process according to the embodiment.

FIG. 13 is a structural diagram of an SSC-LD manufactured in a fourth stage of the manufacturing process according to the embodiment.

FIG. 14 is a structural diagram of the SSC-LD manufactured in the fifth stage of the manufacturing process according to the embodiment.

FIG. 15 is a graph comparing a measurement result and a calculation result of a layer thickness profile used in the present embodiment.

FIG. 16 is a diagram for explaining an embodiment of the present invention.

FIG. 17 is a view illustrating the principle of a method for manufacturing a laser device described in Japanese Patent Application Laid-Open No. 5-327111.

FIG. 18 is an enlarged view of the pattern of the growth blocking film shown in FIG.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 active layer 2 tapered waveguide layer 3 p-InP current blocking layer 4 n-InP current blocking layer 5 p-InP cladding layer 6 p-InGaAs contact layer 7 p electrode 8 n-InP substrate 9 n electrode 10 growth inhibiting film 11 Gaps 21 Semiconductor substrate 22 Mask layer 23 Active layer formation region

────────────────────────────────────────────────── (5) References JP-A-7-176827 (JP, A) Journal of Applied Physics, 78 [9], p. 5373-5386 Journal of Crystal Growth, 51, p. 581-586 1995 (Heisei 7) Autumn Proceedings of the Japan Society for Applied Biology, 26a-ZE-1 p. 179 1999 (Heisei 11) Autumn Proceedings of the Society of Applied Biological Sciences, 3a-ZE-36 p. 978 (58) Field surveyed (Int. Cl. ⁷ , DB name) H01S 5/00-5/50 H01L 27/15

Claims (9)

(57) [Claims] 1. A selective MOVP in which a desired layer is grown in said opening by using a pair of growth-inhibiting films opposed in the y direction with a stripe-shaped opening extending in the x direction on the xy coordinate.
A method for designing a semiconductor optical element manufactured by E growth method, the growth rate at a sufficiently distant to R∞ from growth arrest film, local growth rates R _o, L _xdiff and L _Ydisff respectively x and y directions The diffusion length of τ (x, y) is the material life,
The growth rates R _x (x) and R _y (y) of the growth layer in the x direction and the y direction at the opening are respectively represented by the following one-dimensional diffusion equation: (L _xdiff ) ² · τ (x) · ｛d ² R _x (x) / dx ² ｝ = R _x (x) −R _o (x) (Equation 1); and (L _ydiff ) ² · τ (y) · {d ² R _y (y ) / Dy ² ｝ = R _y (y) −R∞ (Equation 2), and is locally determined from the R _x (x) and R _y (y) and a desired layer thickness profile. A method for designing a semiconductor optical device, comprising: obtaining a selective growth rate; and obtaining a profile of a selective growth mask based on the local growth rate. 2. The method according to claim 1, wherein the width of the opening is 2 μm or less. 3. A growth rate R _{y in the} y-direction instead of Equation 2.
3. The method according to claim 1, wherein (y) is obtained from an experimental result. 4. The growth rate R _y (y) in the y direction is given by
3. The method for designing a semiconductor optical device according to claim 1, wherein the value is obtained by solving the following equation. 5. A growth layer for a light emitting portion and a waveguide portion is selectively grown in said opening by using a pair of growth inhibiting films opposed to each other in a y direction with a stripe-shaped opening extending in the x direction interposed therebetween. In the selective growth method, the growth blocking film has a first portion and a second portion sequentially arranged in the x direction corresponding to a light emitting portion and a waveguide portion to be formed, respectively. A first having a substantially flat width
And a wide region having a width wider than the first flat width region following the first flat width region, wherein the second portion has a width larger than that of the first flat width region. A selective growth method having a narrow second flat width region. 6. The selective growth method according to claim 5, wherein a boundary between the first flat width region and the wide region is step-shaped. 7. A growth layer for a light emitting section and a waveguide section is selectively grown in said opening by using a pair of growth inhibiting films opposed to each other in a y direction with a striped opening extending in the x direction interposed therebetween. In the selective growth method, the growth blocking film has a first portion and a second portion sequentially arranged in the x direction corresponding to a light emitting portion and a waveguide portion to be formed, respectively. A flat-width region having a substantially flat width; and a wide-width region following the flat-width region and increasing in width toward a second portion, wherein the second portion has a width that increases with distance from a boundary with the first portion. A selective growth method characterized by having a narrow region in which the width of the substrate is reduced. 8. Assuming that the width of the flat width region is W, the length of the widened region is 0.1 W to 10 W and the maximum width is 1.
2 W to 3 W, and the length of the narrow region is 2 W to 20 W.
The selection method according to claim 7, wherein the width of the terminal is 0.2 W or less. 9. The length of the widened area is 0.3 W to 0.7 W
9. The selection method according to claim 8, wherein the maximum width of W is 1.3W to 1.7W, and the length of the narrow region is 7W to 9W.