JP2742358B2 - Semiconductor photodetector 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 semiconductor photodetector having a pn junction in a semiconductor and capable of reducing a parasitic resistance by an ohmic electrode and capable of high-speed response, and a method of manufacturing the same.

[0002]

2. Description of the Related Art A conventional general semiconductor photodetector has a core layer 303 as a light absorption layer having a low carrier concentration as shown in FIG.
An upper clad layer 304 as a p-type conductive layer and a lower clad layer 302 as an n-type conductive layer are arranged above and below (non-doped InGaAs in the case of FIG. 3), respectively. High-speed GaInAs with reduced resistance
/ InP PIN Photodiode "Proceedings of the Spring Meeting of the Japan Society of Applied Physics, 1991, 953 pages, 28p-F-
1). In the semiconductor photodetector, the p-type conductive layer 30
4 between the n-type conductive layer 302 and the n-type conductive layer 302 to form a depletion layer in the non-doped light absorbing layer 303;
By utilizing the high electric field applied to the depletion layer, signal light incident on the light absorption layer 303 from the upper surface or the back surface of the semiconductor photodetector is photoelectrically converted.

Incidentally, the response speed of the semiconductor photodetector is determined by the CR time constant and the traveling time of the photoexcited carriers. In order to reduce the transit time of photoexcited carriers, it is necessary to reduce the thickness of the core layer 303, which is a light absorption layer.
In order to suppress the increase, the area of the core layer 303 must be reduced.

[0004]

However, since it is necessary to form a p-type ohmic electrode 307 on a part of the upper surface of the upper p-type cladding layer 304 as shown in FIG. When the area of the core layer 303 is reduced, the area of the p-type ohmic electrode 307 is inevitably reduced, and as a result, the ohmic resistance R increases and the CR time constant decreases. There was a problem that high speed response was not possible after all.

SUMMARY OF THE INVENTION An object of the present invention is to provide a semiconductor photodetector capable of resolving an increase in ohmic resistance and responding at high speed.

[0006]

SUMMARY OF THE INVENTION In order to achieve this object,
Therefore, in the present invention, the upper surface provided on the semiconductor substrate
At least the partial cladding layer, the core layer, and the lower cladding layer
In a waveguide type semiconductor photodetector having three layers,
The width of the core layer, the width of the upper cladding layer and the
The upper cladding layer is formed narrower than the electrode width.

Further , an upper clamp provided on a semiconductor substrate is provided.
At least three of a lad layer, a core layer, and a lower cladding layer
Having a width of the core layer, the width of the upper cladding layer
Formed narrower than the width and electrode width of the upper cladding layer
Of manufacturing a fabricated waveguide type semiconductor photodetector
Te, a step of laminating the three layers, forming a stripe-shaped etching mask to the photodetector layer,
Irradiating the ion beam from above the etching mask and inclining the irradiation direction of the ion beam with respect to the lamination direction in a plane perpendicular to the stripe during or during the irradiation interruption.

Further , an upper clamp provided on a semiconductor substrate is provided.
At least three of a lad layer, a core layer, and a lower cladding layer
Having a width of the core layer, the width of the upper cladding layer
Formed narrower than the width and electrode width of the upper cladding layer
Of manufacturing a fabricated waveguide type semiconductor photodetector
Te, a step of forming the lower clad layer on said semiconductor substrate, said upper clad layer, a step of only a portion growing the core layer to form a selective growth mask is Apertures, above the Apertures portion Laminating a core layer and the upper clad layer.

[0009]

According to the present invention, there is provided a semiconductor photodetector and a method of manufacturing the same.
In comparison with the conventional semiconductor photodetector composed of an upper cladding layer and a core layer having substantially the same width,
Since the ohmic resistance can be reduced,
The constant can be reduced.

[0010]

Example will be described an embodiment of the present invention in conjunction with the accompanying drawings. FIG. 1 is an external view showing an embodiment of a semiconductor photodetector according to the present invention, and FIG. 2 is a manufacturing process of the semiconductor photodetector shown in FIG.
It is a diagram showing a degree.

FIG. 1 shows an embodiment of a waveguide type photodetector as a semiconductor photodetector of the present invention. In FIG. 1, 101 is a semi-insulating InP substrate, 102 is a lower cladding layer which is an n-type InP lower conductive layer, 103 Is a core layer which is a non-doped InGaAs light absorbing layer, 104 is an upper cladding layer which is a p-type InP upper conductive layer, 105 is a selective growth mask, 106 is an n-type ohmic electrode, and 107 is a p-type ohmic electrode. The n-type InP lower conductive layer 102 serves as a lower cladding layer together with the InP substrate 101, the non-doped InGaAs light absorbing layer 103 serves as a core layer, and the p-type InP upper conductive layer 10 serves as a core layer.
4 functions as an upper cladding layer by forming an optical waveguide, but when viewed as a semiconductor photodetector, it has a pin photodiode configuration in which the non-doped InGaAs light absorbing layer 103 having a low carrier concentration is used as a photoelectric conversion layer. I have. Since the width of the core layer 103, which is the non-doped InGaAs light absorbing layer, is formed to be narrower than the width of the upper cladding layer 104, the p-type ohmic electrode 107 provided on the upper surface of the upper cladding layer 104 is 10
The width in contact with 4 can be made sufficiently wider than the width of the core layer 103. Therefore, capacity, ohmi
The CR time constant can be reduced because the
As a result, a semiconductor photodetector capable of high-speed response can be obtained.

In the above embodiment, the upper cladding layer 104
Although the lower clad layer 102 is formed of an n-type InP conductive layer as a type InP conductive layer, these conductive types may be reversed. In addition, when the upper cladding layer 104 has an upper surface area twice or more as large as the area of the core layer 103 or the lower cladding layer 102, the resistance based on the ohmic electrode can be reduced to about １ ／. , And a faster response becomes possible.

A method of manufacturing a semiconductor photodetector in which the upper surface area of the upper clad layer is formed larger than the area of the core layer as described above is described in Japanese Patent Application No. 4-183490. In order to form the upper cladding layer with a larger upper surface area, it is manufactured according to the following steps. That is, as shown in FIG. 2A, a 0.5 μm thick n-type InP lower cladding layer 102 is epitaxially grown on a semi-insulating InP substrate 101. Next,
As shown in FIG. 2B, an SiO ₂ film 105 is formed on the entire surface of the n-type InP lower cladding layer 102. Thereafter, a part of the SiO ₂ film 105 is etched to
As shown in (c), a selective growth mask is formed by exposing the selective growth region and exposing only the portion where the upper cladding layer 104 and the core layer 103 are to be grown. Next, FIG.
As shown in (d), a core layer 103 as a non-doped InGaAs light absorbing layer having a thickness of 0.3 μm and a p-type InP upper cladding layer 104 having a thickness of 1 μm are sequentially epitaxially grown in a window opening portion of the selective growth mask. . Next, FIG.
As shown in (e), a portion of the SiO ₂ film 105 outside the selective growth region is etched, an n-type ohmic electrode 106 is formed thereon, and the p-type upper cladding layer 10 is further formed.
If a p-type ohmic electrode 107 is formed on almost the entire upper surface of the waveguide 4, a waveguide-type photodetector is realized.

In the epitaxial layer formed by the selective growth in the manufacturing step (d), not only the growth from the upper surface but also the growth from the side surface is promoted. become. as a result,
Upper cladding layer 1 having at least twice the area of core layer 103
04 can be formed. In a semiconductor photodetector actually manufactured by using the present invention, the core layer 103 was 6 μm square and the upper cladding layer 104 was 9 μm square for a selective growth region of 5 μm square .

As a result of forming a p-type ohmic electrode having a width of 3 μm around the upper surface of the upper cladding layer 104, the ohmic resistance is reduced to about で も even though the capacitance is almost the same as that of the conventional semiconductor photodetector. Decrease, response speed is 30GHz
And about twice the performance of the prior art.

In this embodiment, an example is shown in which a material that lattice-matches with the InP substrate is used as the semiconductor material. However, similar effects can be expected even if some or all of these materials do not lattice-match with InP. Further, the signal light wavelength is 1.55
Although the case of μm is exemplified, a waveguide-type semiconductor photodetector having the same effect as that of the present embodiment can be realized for signal light having a wavelength other than 1.55 μm by appropriately selecting the material. it can. Further, the present structure can be applied to another optical element such as a semiconductor laser or a semiconductor optical modulator. In the manufacture of the semiconductor photodetector,
In this case, a stripe is formed on the photodetector layer in which the three layers are stacked.
An etching mask is formed in the shape of
Irradiate the ion beam during irradiation or during irradiation interruption.
The irradiation direction of the electron beam is a striped etching mask.
May be inclined with respect to the stacking direction in a plane perpendicular to the stacking direction.

[0017]

As described above, in the semiconductor photodetector and the method of manufacturing the same according to the present invention , the CR time constant is reduced.
Therefore, a semiconductor photodetector capable of high-speed response can be obtained.

[Brief description of the drawings]

FIG. 1 is an external view showing an embodiment of a semiconductor photodetector according to the present invention.

FIG. 2 shows a manufacturing process of the semiconductor photodetector shown in FIG .
FIG .

FIG. 3 is a schematic diagram showing a conventional semiconductor photodetector.

[Explanation of symbols]

 Reference Signs List 101 semiconductor substrate 102 lower cladding layer (n-type lower conductive layer) 103 core layer (non-doped light absorbing layer) 104 upper cladding layer (p-type upper conductive layer) 105 selective growth mask

Claims (3)

(57) [Claims] 1. A waveguide type semiconductor photodetector having at least three layers of an upper cladding layer, a core layer, and a lower cladding layer provided on a semiconductor substrate, wherein the width of the core layer is equal to the width of the upper layer. A semiconductor photodetector, wherein the width is smaller than the width of the cladding layer and the width of the electrode of the upper cladding layer. 2. An upper cladding provided on a semiconductor substrate.
At least three layers: a layer, a core layer, and a lower cladding layer.
Wherein the width of the core layer is equal to the width of the upper cladding layer.
And the upper cladding layer is formed narrower than the electrode width.
In a method of manufacturing a waveguide-type semiconductor photodetector, a step of stacking the three layers, a step of forming a striped etching mask on the photodetector layer, and a step of forming an ion beam from above the etching mask Irradiating the ion beam during the irradiation or during the interruption of the irradiation, and inclining the irradiation direction of the ion beam in the plane perpendicular to the stripe with respect to the stacking direction. Method. 3. An upper cladding provided on a semiconductor substrate.
At least three layers: a layer, a core layer, and a lower cladding layer.
Wherein the width of the core layer is equal to the width of the upper cladding layer.
And the upper cladding layer is formed narrower than the electrode width.
In a method of manufacturing a waveguide-type semiconductor photodetector, a step of forming the lower clad layer on the semiconductor substrate, and a selective growth mask in which only the upper clad layer and the core layer are grown. And a step of laminating the core layer and the upper clad layer on the windowed portion. A method for manufacturing a semiconductor photodetector, comprising: