JPH0250487A - Semiconductor photodetecting element - Google Patents

Abstract

PURPOSE:To selectively photoelectrically convert efficiently a plurality of specific wavelength lights by providing a plurality of different band gap energy bands in one absorption layer, and a plurality of electrodes for externally leading a photoelectric conversion current generated at each energy band. CONSTITUTION:A p<+> type InP layer 2, an N-type InP avalanche region layer 3 and an N-type InGaAs absorption layer 4 provided with an electrode terminal 6 on its top are sequentially formed on a p+ type InP substrate 1 provided with an electrode terminal 5 in its bottom. Electrodes 7-9 are provided in response to the difference of band gap energies in the absorption layer at the layer 4, and the energy bands are so formed between a conduction band 12 and a valence band 11 as to respond to input wavelength lights 18-20. Thus, a plurality of specific wavelength lights can be selectively photoelectrically converted efficiently.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a semiconductor light-receiving device, and more particularly to a semiconductor light-receiving device having a function of absorbing and receiving multi-wavelength input light for use in optical communication wavelength division multiplexing systems.

[Conventional technology]

Conventionally, in this type of semiconductor light-receiving device, photocurrent conversion is performed through one semiconductor light absorption layer.

FIGS. 5(a) and 5(b) respectively show a plan view and a sectional view taken along line AA' of a typical structure of a conventional semiconductor light-receiving element, and as is clear from the drawings, the structure is
For example, a P+ type InP substrate 1 with an electrode terminal 5 provided on the bottom, a P+ type InP 2, an n-type InP avalanche region layer 3, and an n-type InGaAs substrate with an electrode terminal provided on the top.
It has a four-layer structure including an absorption layer 4, and the n-type InGaAs absorption layer 4 is excited by incident light from the light-receiving surface 10 to generate a photoelectric conversion current within the layer. Here, electrode terminals 5 and 6
supply the power supply voltage, respectively.

As shown in FIG. 6, this type of semiconductor light-receiving element has only one bandgap energy band 33 in one absorption layer, and receives light of various bandwidths all at once.

That is, electrons 34 in the valence band 31 are exposed to 1200 nm light 36, 1300 nm light 37, and 1500 nm light 3.
8 and are excited to the bandgap energy band 33 of the conduction band 32, respectively. For this reason, a filter or the like is installed when only light with a specific bandwidth is to be received, and in an optical communication system using multi-wavelength light, a plurality of semiconductor elements are provided to receive light with such a characteristic bandwidth.

[Problem to be solved by the invention]

The conventional semiconductor light-receiving device described above has only one bandgap energy band inside the absorption layer inside the device, so the absorption characteristics of this absorption layer are set over a wide range with respect to the light receiving wavelength to widen the light receiving band considerably. This is usually set.

FIGS. 7 and 8 are diagrams showing the absorption characteristics and photoelectric conversion characteristics of the light absorption layer for the received light wavelength in a conventional semiconductor photodetector, respectively.As is clear from FIG. Type 1nGaAs absorption layer 4
are the typical receiving wavelength λI (1200 nm), λt (1
300 nm) and λ.

They each show good absorption coefficients (K) for photon energy (E) of (1500 nm).

Therefore, if we summarize this as shown in Table 1, the conventional n-type I
As is clear from FIG. 8, it is understood that the nGaAs absorption layer 4 efficiently photoelectrically converts each wavelength light in the above band.

However, in the field of systems such as optical communication or optical measurement, which require light reception only in a specific wavelength band, it is rather required that the light reception band be narrow. However, meeting this requirement with only one absorbent layer involves technical difficulties, and at present, this has been solved by the use of filters, splinters, etc. Therefore, optical communication systems that use multi-wavelength light require multiple light-receiving elements equipped with such filters, which increases the size of the system equipment, making it impossible to reduce costs, and reducing conversion efficiency. We cannot expect quality improvement.

In view of the above circumstances, an object of the present invention is to provide a semiconductor light-receiving element that can selectively and efficiently photoelectrically convert light of a plurality of specific wavelengths.

[Means to solve the problem]

The semiconductor light-receiving device of the present invention has a plurality of different bandgap energy bands in one absorption layer and a plurality of electrodes for leading outside the photoelectric conversion current generated for each bandgap energy band, and It has the ability to absorb and receive light of each wavelength simultaneously and independently in the bandgap energy band corresponding to the .

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1(a) is a plan view showing an embodiment of the semiconductor light receiving element of the present invention. FIG. 1(b) shows the AA' cross-sectional structure of the semiconductor light receiving element of FIG. 1(a). Figure 1(b)
, a P+ type InP layer 2, an n-type InP avalanche region layer 3, and an n-type InG layer 3 having an electrode terminal 6 provided on the top are formed on a P+ type InP substrate l having an electrode terminal 5 provided on the bottom.
An aAs absorption layer 4 is formed. The n-type InGaAs absorption layer 4 is provided with electrodes 7, 8.9 depending on the difference in band gap energy within the absorption layer.

Next, the energy bands in the n-type I n Ga As absorption layer 4 will be explained with reference to FIG. 2.

The bandgap energy band within the n-type InGaAs absorption layer 4 is such that it responds to each input wavelength light 18, 19, 20.
It is formed between the conduction band 12 and the valence band 11. This is achieved by creating a stepped impurity concentration within the absorption layer.

The light 18 having a wavelength of 1200 nm excites the electrons 16 in the valence band 11 before being absorbed by the band gap energy 15 only. Further, the light 19 with a wavelength of 1300 r+m excites the electrons 16 in the valence band 1 before light absorption to only the band gap energy 14.

The light 20 with a wavelength of 1500 nm moves the electrons 16 in the valence band 11 before light absorption to the band gap energy 13.
Excite only.

That is, as shown in Table 2, the n-type InGaAs absorption layer 4
The bandgap energy of 13,14゜15 is the specific reception wavelength λ, 1200 nm, λ, 1300 nm, λ
, 1500 nm, wavelength dependence is given to each absorption/transmission characteristic.

(Absorption/transmission state of each wavelength in the absorption layer) ○: Light absorption ×: Light transmission ＼: Wavelengths greater than the absorption wavelength are not input. Therefore, the wavelength λ1. Multi-wavelength input light consisting of λ2゜λ, has a bandgap energy band 13 corresponding to the energy of the wavelength λ1, a bandgap energy band 14 corresponding to the energy of the wavelength λ2, a bandgap energy band 14 corresponding to the energy of the wavelength λ, and a bandgap energy band 13 corresponding to the energy of the wavelength λ2. Each valence band electron is excited to the energy band 15.

Therefore, there is one electrode 7 in the n-type InGaAs absorption layer 4 shown in FIG. 1(b) so as to respond to each input wavelength.
The electrode 8 is set to receive 200 nm light, the electrode 8 is set to receive 1300 nm light, and the electrode 9 is set to receive 1500 nm light.
There is.

FIG. 3 shows the bandgap energy band of FIG. 2 in terms of the wavelength (photon energy) dependence of the absorption coefficient. In the n-type InGaAs absorption layer, a step-like band gap energy band is formed, so
The respective absorption characteristics show a characteristic curve 24 for light 21 with a wavelength of 1200 r+m, a characteristic curve 25 for light 22 with a wavelength of 1300 nm, and a characteristic curve 26 for light 23 with a wavelength of 1500 nm.

FIG. 4 shows the wavelength sensitivity characteristics extracted from each electrode 7, 8.9 in FIG. 1200nm light 2 from electrode 7
The characteristic curve 27 corresponding to 1 is 1300 nm from the electrode 8.
A characteristic curve 28 corresponding to the light 22 extends from the electrode 9 to 1500
A characteristic curve 29 corresponding to nm light 23 is obtained.

〔Effect of the invention〕

As explained above, by providing different bandgap energy bands in one absorption layer of a semiconductor photodetector, the present invention can simultaneously and independently absorb and receive each wavelength of input light of multiple wavelengths. This has the effect of making it possible to realize an optical communication system using multiple wavelengths without having to do so.

[Brief explanation of the drawing]

FIG. 1(a) is a plan view of the semiconductor photodetector of the present invention.
Figure (b) is an AA' cross-sectional view of the semiconductor photodetector shown in Figure 1(a), Figure 2 is a diagram showing the bandgap energy band within the absorption layer of the semiconductor photodetector of the present invention, and Figure 3 4 is a diagram showing the wavelength dependence of the absorption coefficient, FIG. 4 is a diagram showing the sensitivity characteristics of the received wavelength, FIG. Figure 6 is a diagram showing the bandgap energy band in the absorption layer of a conventional semiconductor photodetector, and Figure 7 is a diagram showing the absorption coefficient of the conventional semiconductor photodetector. FIG. 8, a diagram showing wavelength dependence, is a diagram showing wavelength sensitivity characteristics of a conventional semiconductor light-receiving element. l...P type InP substrate, 2...P type I
nP layer, 3... n-type InP avalanche region layer, 4... n-type InGaAs absorption layer, 5, 6...
... Electrode terminal, 7.8.9 ... Electrode, 10
...... Light-receiving surface, 11°31... Valence band, 12,32... Conduction band, 13.14,15.
33...Band gap energy band, 16.
34...Electron before light absorption, 17,3...
・Electrons after light absorption, 18, 21, 36.41...
・Wavelength 1200nm light, 19, 22, 37.42...
...Wavelength 1300nm light, 20,23,38.43・
...wavelength 1500nm light, 24, 25, 26.4
4...Absorption curve, 27, 28.29...
・Wavelength sensitivity characteristic curve. Agent Patent Attorney Susumu Uchihara (b No. 1 (α) (b) Fig. S Photon energy - (S1 and 5, 4 ←) Fig. 3 Fig. 4

Claims (1)

[Claims] A semiconductor substrate, a semiconductor absorption layer formed on the semiconductor substrate and having a plurality of bandgap energy bands each selectively absorbing photon energy components in different wavelength bands, and a photoelectric conversion current generated for each bandgap energy band. 1. A semiconductor light-receiving element, comprising: a plurality of electrodes, each of which leads to the outside.