JPH02170581A - Semiconductor photodetective device - Google Patents

Abstract

PURPOSE:To obtain a wavelength selection function integrated on a single semiconductor substrate by a method wherein a narrow band pass filter formed of a semiconductor multilayer film is constituted inside an i-type region of a pin photodiode. CONSTITUTION:An i-type or a high resistivity region 2 contains a light absorbing layer 3 formed of a semiconductor whose band gap wavelength is narrow and a narrow band pass filter 4 formed of a semiconductor layer transmissive to a optical signal wavelength. The narrow band pass filter 4 is provided with a center cavity region 7, which determines a transmissive wavelength, arranged at its center and multilayer reflective layers 5 and 7, which are composed of semiconductor layers of high refractive index and other semiconductor layers of relatively low refractive index that are alternately laminated, arranged on the sides of the center cavity region 7 respectively. And, a load R and a variable reverse bias voltage source Vr are connected between a p-type region 8 and an n-type region 1. Therefore, the selection wavelength lambda1 of the narrow band pass filter 4 can be varied by making the reverse bias voltage Vr variable. By this setup, a wavelength selecting function can be obtained.

Description

[Detailed Description of the Invention] [Summary] Regarding a semiconductor light receiving device having a wavelength selection function, an object of the present invention is to provide a semiconductor light receiving device having a wavelength selection function integrated on a single semiconductor substrate. , a pin type semiconductor light receiving device comprising a high resistivity region including a light absorption layer, a P type region, and a light incidence surface, wherein the high resistivity region is provided between the light incidence surface and the light absorption layer. is configured to have a narrow bandpass filter including a central cavity region and a multilayer reflective layer consisting of a plurality of laminated layers of pairs of high refractive index layers and low refractive index layers disposed on both sides of the central cavity region.

[Industrial Field of Application] The present invention relates to a semiconductor light receiving device, and more particularly to a semiconductor light receiving device having wavelength selection R capability.

Semiconductors absorb light with photon energy higher than the bandgap energy. By utilizing electron-hole pairs generated during light absorption, photoconductive type, photovoltaic type, etc. photodetection can be performed. In particular, pin-type photodiodes are widely used, which have a pin diode structure, form an electric field in the i-type layer, and use the electric field to draw out electron-hole pairs generated by light absorption in the i-type layer in opposite directions and extract them as photocurrent. It's being used.

On the other hand, in optical communication, since light of a predetermined wavelength (photon energy) is used, it is desirable to detect only light of a specific wavelength.

[Prior Art] In optical communications, it is desirable to select and receive light in a wavelength range of about 1 degree or less from a wavelength range of about 50 people, for example.

FIGS. 2A and 2B show examples of wavelength selective light reception according to the prior art.

In FIG. 2(A), the incident light 50 is transmitted through the lenses 51 and 52.
, collimated by the slit 53 and incident on the grading 54. The light 56 reflected from the grading 54 undergoes angular wavelength dispersion due to interference, and becomes monochromatic by passing through the slit 57. This monochromatic light 58 is transmitted to the ρin photodiode 6 using a lens 59 etc.
0. The pin photodiode 60 includes, for example, an n-type 1nP substrate 63, a light absorption layer 62 made of an n-type high-resistivity InGaAs layer grown on the substrate 63, and a window region 53 made of a P-type 1nP layer grown thereon. has. InP is a transparent material for communication wavelength light in the 1.55 μ band, and only the light absorption layer 62 of InGaAs absorbs the light.

When the grating 54 is rotated, the wavelength of the light emitted from the wavelength slit 57 changes. In this manner, only light of a desired wavelength is incident on the photodiode 60, thereby performing light reception with wavelength selection.

In FIG. 2, (B), incident light is made monochromatic through a narrow band pass filter 65 formed on a glass substrate, and the monochromatic light is sent through a lens 66 to a pin photodiode 6.
It is incident on 0. The pin photodiode 60 is the second
It is similar to that in Figure (A).

The configuration shown in FIG. 2(A) has a wavelength selection function, and the selected wavelength can be changed by rotating the grating 54.

The configuration shown in FIG. 2(B) has a wavelength selection function, but cannot change the selected wavelength, and has a relatively simple configuration and can be made small.

[Problems to be Solved by the Invention] In optical communications, there is a desire to make a light receiver having a wavelength selection function as small as possible.

The configuration of FIG. 2(A) requires an extremely large device, and even the relatively simple configuration of FIG. 2(B) requires the use of multiple parts.

An object of the present invention is to provide a semiconductor photodetector having a wavelength selection function integrated on a single semiconductor substrate.

Furthermore, the emission wavelength of a light emitting device such as a laser used for optical communication varies slightly (for example, by about 5 widths) depending on the manufacturing conditions of the light emitting device. It is desirable to be able to tune the light receiving device to this variation in emission wavelength.

If the wavelength could be changed over a wider wavelength range, it would be extremely effective for tuned light reception in multiplexed optical communications.

Although the configuration of FIG. 2(A) allows the selection wavelength to be changed freely, the apparatus is large-scale. Although the configuration of FIG. 2(B) can be made relatively compact, the selected wavelength is fixed. In order to vary the selected wavelength within a certain range, it is necessary to provide a number of narrow band pass filters that cover the wavelength range.

An object of the present invention is to provide a semiconductor light receiving device that can be integrated on a single semiconductor substrate, has a wavelength selection function, and can change the selected wavelength.

[Means for Solving the Problems] The basic concept of the present invention is to configure a narrow bandpass filter using a semiconductor multilayer film within the i-shaped head area of a pin photodiode.

FIGS. 1A, 1B, and 1C are explanatory diagrams of the principle of the present invention.

FIG. 1(A) is a sectional view showing the structure of a photodiode type semiconductor light receiving device according to the present invention. An n-type region 1, an i-type or high resistivity region 2, and a p-type region 3 form a ρin photodiode structure.

This i-type or high resistivity region 2 includes a light absorption layer 3 made of a semiconductor with a narrow bandgap wavelength and a narrow bandpass filter 4 made of a semiconductor layer that is transparent at the signal light wavelength.
The narrow bandpass filter 4 includes a central cavity region 6 that defines a transmission wavelength, and a semiconductor layer having a relatively high refractive index and a semiconductor layer having a relatively low refractive index are alternately arranged on both sides of the central cavity region 6 . 5.7 A multilayer reflective layer formed by laminating the
are placed. A light entrance surface 9 is formed on the upper surface. A load R and a variable reverse bias voltage source Vr are connected between p-type region 8 and n-type region 1. Note that the p-type region and the n-type head region may be interchanged.

[Function] This narrow band pass filter 4 has transmittance characteristics as shown in FIG. 1(B). The center wavelength λ1 of the transmission band is selected according to the optical path length of the central cavity region 6, and the height and width of the transmission band are determined according to the refractive index ratio and the number of layers of the high refractive index semiconductor and the low refractive index semiconductor laminated on both sides.

By applying a reverse bias to this pin photodiode structure as shown in FIG. 1(A), an electric field is generated in the i-type or high resistivity region 2, and the light is absorbed by the light absorption layer 3 for optical excitation. When carriers are generated, they are guided to the ρ-type region 8 and the n-type region 1 according to the electric field. The current flowing in this manner changes the voltage drop across the load R to provide an output signal.

High resistivity region 2 when changing the reverse bias applied to the semiconductor
The electric field strength inside changes. The semiconductor constituting the bandpass filter 4 exhibits the 7-Landz-Gerdeisch effect due to a reverse bias electric field, increasing its refractive index as shown in FIG. 1(C). As the refractive index increases, the optical path length of each layer increases, and the filter characteristics shift toward longer wavelengths, as shown by the arrow in FIG. 1(B). By making the reverse bias voltage Vr variable in this manner, the selected wavelength λ1 of the narrow bandpass filter 4 can be changed.

``Example'' Figures 3 (A), (B), and (C) show examples of the present invention.

In FIG. 3(A), 11 is an n++1nP substrate, 12
is n-type (e.g. n≦1~10”cl-3, thickness 2μ
13 is an n-type 1nP layer with a relatively low refractive index (e.g. n≦~lX1).
014C "3, thickness ~ 0.122 μm) and phase (e.g. n
≦~1×1014cl-3, thickness~0.111μm, y
'; 0.9) is alternately grown in about 10 or more layers, preferably about 40 layers, and 14 is a low refractive index InP layer (
For example n≦~1 x 10” crn-3 thickness ~0.2
35 μm), 15 is 13
16 is an InP know-wind layer (
For example, n~IX1lX1015cI thickness 0.5 μm),
17 is a p+ type scattered layer that does not diffuse Zn. On the substrate 11 are an Au/Ge-^U n-side electrode 18 and a P-type diffusion layer 17.
A ρ side electrode 19 of Ti/Pt/Aυ is formed thereon.

The multilayer reflective layer 13.15 and the central cavity layer 14 form a narrow bandpass filter 2o. The refractive index of InP is approximately 3.1, and the refractive index of InGaAsP is approximately 3°6.
It is. The central cavity layer 14 has an optical path length of λ/2, and the multilayer reflective layers 13.15 on both sides are in contact with the central cavity layer 14 and have a thickness corresponding to an optical path length of λ/4 (λ/4 thickness).
, a high refractive index layer having a thickness of λ/4, a low refractive index layer having a thickness of λ/4, and a repeating stack of this pair.

The light absorption layer 12 has a suitable absorption coefficient at the communication light wavelength and has a composition that is lattice matched to InP of the substrate. For example, donor 4 is selected.
It is composed of a layer with a thickness of about 2 .mu.m and a thickness of less than I.times.10"C11-3.

Unnecessary parts of the surface are protected with Si3N4 or the like. Light enters from the top surface, passes through the p-type region 17, the window layer 16,
After being wavelength-selected to a predetermined wavelength width by the narrow bandpass filter 20, the light enters the light absorption layer 12 and is absorbed. Photoexcited carriers are detected as photoexcited current. Light of other wavelengths is reflected by the narrow bandpass filter 20.

FIG. 3(B) shows the external appearance of this semiconductor light receiving device, and shows a semiconductor chip 24 on which a light receiving device is formed on a metal stem 22.
is bonded with the In layer 26, and pHl! A gold wire 28 is bonded to the It electrode. Signal light enters through an optical fiber 30 from above the entrance plane.

FIG. 3(C) shows the receiving sensitivity characteristics of the semiconductor light receiving device with a built-in filter constructed in this way.

The horizontal axis shows wavelength, and the vertical axis shows relative receiving sensitivity.

Each of the multilayer reflective layers 13.15 has a refractive index nH=3.
6. Characteristics when 30 layers of high refractive index layers with thickness d H = 0, 108 μm and low refractive index layers with refractive index n = 3.13, thickness d, = 0.12 [8 μm are laminated alternately It is.

The wavelength characteristic, which has a center wavelength of 15,500 nm with no bias, shifts to a center wavelength of 15,501.5 nm with a reverse bias of 30V. Note that the half width is approximately 0.8 degrees.

By changing the structure of the multilayer reflective layer, the filter characteristics can be further changed.4 For example, when the number of layers is increased, the half-width becomes narrower. In this way, according to the above-described embodiment, light having a wavelength of about 1.55 μm can be selectively received with a half-width of about 0.5 degrees.

Furthermore, by changing the applied bias voltage, the reception wavelength can be changed by about ±5.

FIG. 4 shows another embodiment of the present invention. FIG.
The InP type wind layer 16 has a thickness of about 2 μm, and has a thickness of 2n.
p+ type scattered layer 17 in which about 1×1018 CI-3 is diffused.
It is formed to a depth of about 1.7 μm, and a wind layer 16 is formed below it.
About 1.3 μm was left.

Surrounding this p+ type scattering layer 17 is an acceptor concentration of 1 x
A guard ring head 32 of about 1016 cm-3 is formed by ion implantation. A 513N4 film 34 is also provided on the entrance surface.

The case where InGaAs is used as a light absorption layer, InGaAsP is a high refractive index material, and InP is used as a low refractive index material on a 1nP substrate has been described above, but it is obvious that there are many other possible combinations.

For example, on a GaAS substrate, GaAs is used as a light absorption layer,
AlGaAs having different compositions can be used as a high refractive index material and a low refractive index material.

In addition, GaSb is used as a substrate and a light absorption layer, and A with a different composition is used.
GaAsSb can also be used as a high refractive index material or a low refractive index material.Although the above six embodiments have been described, it is obvious to those skilled in the art that various changes, modifications, combinations, etc. can be made within the scope of the present invention. Dew.

[Effects of the Invention] As described above, a narrow band pass filter having a sufficiently narrow transmission band can be incorporated into a semiconductor light receiving device manufactured on a single substrate, and a semiconductor light receiving device having a wavelength selection function can be obtained.

Furthermore, by applying a reverse bias to yIN, the selected wavelength can be variably controlled.

[Brief explanation of the drawing]

Figures 1 (A), (B), and (C) are diagrams explaining the principle of the present invention, where (A) is a cross-sectional view, (B) is a graph of filter characteristics, and (C) explains the Franz Gerdeisch effect. 2 (A) and 2 (B) show the conventional technology, (A) is a diagram showing wavelength selection by a grating, (B) is a diagram showing wavelength selection by a glass substrate narrow band pass filter, 3 (A>, (B), and (C) show examples of the present invention, (A) is a cross-sectional view, (B) is an external view, and (C) is a graph of wavelength-dependent receiving sensitivity characteristics. The fourth factor is a cross-sectional view showing another embodiment of the present invention. In the figure, ■ n-type regions 5, 13, 18, i-type (high refractive index) region light absorption layer narrow band pass filter multilayer reflective layer central cavity region ρ-shaped head region entrance surface substrate light absorption layer multilayer reflective layer central cavity layer wind layer ρ”-shaped diffusion layer electrode stem gold wire optical fiber (A) two wavelength selection by bulleting (B) two wavelength selection by narrow band pass filter Conventional technology No. Figure 2 (A>Cross section Figure 3 (Preliminary 1) Director of the Japan Patent Office i, *Indication of Patent Application No. 326693 of 1988 Name of the invention Semiconductor photoreceptor device 3° Amendment person Related to the case Postal code

Claims (1)

[Claims] [1], n-type region (1), high resistivity region (2) with light absorption layer (3), p-type region (8) and light incidence surface (9)
A pin-type semiconductor light receiving device comprising: between the light incident surface and the light absorption layer, the high resistivity region is
A semiconductor characterized by having a narrow bandpass filter (2) comprising a central cavity region (6) and a multilayer reflective layer consisting of a plurality of stacked layers of pairs of high refractive index layers and low refractive index layers arranged on both sides of the central cavity region (6). Light receiving device. [2] A variable reverse bias is applied to the high resistivity region (2) via the n-type region (1) and the p-type region (8), and the narrow bandpass filter is controlled depending on the magnitude of the applied reverse bias. 2. The semiconductor light receiving device according to claim 1, wherein the center wavelength of the transmitted light is controlled.