JPS6259895B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a semiconductor light receiving device, and more particularly to a semiconductor light receiving element having wide wavelength characteristics.

In the detection of optical signals in optical spectrum analyzers, multi-wavelength optical communications, etc., a single semiconductor photodetector element such as Si, Ge, GaAs or a multi-component compound semiconductor such as GaAlAs, InGaAsP, PbSnTe, etc.
It is difficult to cover a sufficiently wide wavelength range with HgCdTe etc. alone. Therefore, for photodetection, it is necessary to use a plurality of photodetectors with different wavelength characteristics.

As is well known, multi-component semiconductors, such as binary compounds AB and AC (here, A,
B and C represent arbitrary compounds. ), the band gap Eg of a ternary compound semiconductor such as B _1-x C _x A (B _1-x C _x A) is generally the band gap Eg of each binary compound semiconductor.
It is possible to take any value between (AB) and Eg (AC). For example, ternary compound semiconductor
In Hg _1-x Cd _x Te, HgHe's 0eV as shown in Figure 1.
It is possible to select any band gap depending on "x" between (x = 0) and 1.5eV (x = 1) of CdTe. In the figure, Eg indicates a band gap, and λ _c indicates a received light wave. This kind of thing is 3
The same applies to the elemental compound semiconductor Al _1-x Ga _x As and the quaternary compound semiconductor In _1-x Ga _x As _y P _1-y .

By utilizing these properties of multi-component semiconductors, it is possible to create photodetecting elements with any bandgap, or in other words, any wavelength sensitivity characteristics.

Multi-wavelength photodetecting elements conventionally used utilize the characteristics of multi-component compound semiconductors as described above, and examples of their practical configurations are shown in FIGS. 2a and 2b.

Figure a shows a structure in which a plurality of elements with different wavelength characteristics are stacked in a stack. That is, for example
Taking Hg _1-x Cd _x Te as an example, Hg _1-x1 Cd _x1 Te2 and Hg _1-x2 Cd _x2 Te3 with different x are bonded together on a substrate 1 using a transparent epoxy resin 4. Hg _1-x1 Cd _x1 Te2
On top are indium electrodes 5,5', Hg _1-x2 Cd _x2 Te3
Indium electrodes 6 and 6' are formed thereon, respectively. Further, 7 indicates a light receiving section. However, in this case, it is necessary that x ₁ <x ₂ . In this way, a multi-wavelength photodetecting element with different wavelength characteristics is formed.

Figure b shows an arrayed multi-wavelength sensing element in which multiple elements with different wavelength characteristics are arranged in parallel.
. . . 11 is formed via an adhesive 12, and electrodes 13, 13', 1 are formed on the semiconductors 9, 10, . . . 11.
4, 14', . . . 15, 15' are formed. In the cases shown in FIGS. 2a and 2b, since the photodetecting element has a resin adhesive structure, it has various drawbacks such as low mechanical strength and a complicated manufacturing process.

The present invention provides a multi-wavelength photodetecting element having a monolithic structure that eliminates the above-mentioned drawbacks of the prior art. In other words, the multi-wavelength photodetecting element of the present invention is a multi-wavelength photodetector that can simplify and improve the reliability of optical receiving systems in various optical systems by covering a wide wavelength range with a single element. We aim to provide the following.

Hereinafter, the configuration of the present invention will be explained using the drawings.
First, in the present invention, multicomponent compound semiconductors having different values of x, for example, are sequentially epitaxially grown in multiple layers on a substrate capable of epitaxial growth of a multicomponent compound semiconductor crystal to be used. In this case, the epitaxial layers may be stacked in any order, but from the viewpoint of light receiving efficiency, it is better to stack the epitaxial layers in order from the substrate surface, from the smallest bandgap to the largest bandgap. Also, the thickness of each layer is determined by the wavelength λ _g = corresponding to the band gap Eg of each layer.
When the absorption coefficient α is 1.24/Eg, it is desirable to have at least 1/α or more, and generally 1
The value is between ~10 μm.

The following is an example of forming a multi-wavelength photodetecting element using In _1-x Ga _x As _y P _1-y quaternary compound semiconductors 16 to 19, which can detect light over a wide range of wavelengths from about 1.7 μm to 0.9 μm. This will also be explained with reference to the embodiment shown in FIG. As shown in Figure 3a, on the InP substrate 16
In _1-x1 Ga _x1 As _y1 P _1-y (x ₁ = 0.21, y ₁ = 0.45) 1
7. In _1-x2 Ga _x2 As _y2 P _1-y2 (x ₂ = 0.33, y ₂ = 0.71)
18, In _1-x3 Ga _x3 As _y3 P _1-y3 (x ₃ = 0.47, y ₃ = 1.0)
19 are epitaxially formed in sequence. Although the liquid phase method is typically used to form the epitaxial layer, any method such as the vapor phase method or MBE method may be used. It is important to remove impurities to achieve high purity. Also, the thickness of each layer depends on the ease of manufacturing,
In view of light absorption, etc., 2 to 5 μm is appropriate.

Next, as shown in FIG.
Each of the layers 7 to 19 is shaped so that a portion thereof appears on the surface to form light receiving surfaces 20 to 23 for each wavelength. Thereafter, Au/Sn electrodes 24 and 25 are formed using a normal vapor deposition method to complete the process, as shown in FIG.

In this way, in the multi-wavelength photodetecting element according to this embodiment, the electrodes 24, 25 and In _1-x1 Ga _x1 As _y1 P _1-y1
The sensing element constituted by 17 and the sensing element constituted by electrodes 24, 25 and In _1-x2 Ga _x2 As _y2 P _1-y2 18 are connected in parallel. Here, in the multi-wavelength detection element shown in this embodiment, since each of the light-receiving layers 16 to 19 are all formed of the common electrodes 24 and 25, it is unclear which light-receiving part is receiving light, and the overall I can only get the signal as . However, in the detection elements shown in FIGS. 4 and 5, the electrodes of each light receiving part are separated, so
It is possible to determine which light receiving section is receiving light. That is, the electrodes 24 and 25 shown in FIG.
24b, 24c, 24d, 25a, 25b, 25
Separated images are shown in c and 25d. In addition, in the detection element shown in FIG. 5, insulating grooves 26 are provided not only at the electrodes 24 and 25 but also at the boundaries of the light receiving sections 20 to 23 to prevent signals from adjacent light receiving sections from entering. It also becomes possible to determine whether the wavelength light is actually being received.
In FIGS. 4 and 5, the same numbers as in FIG. 3 indicate the same parts.

FIG. 6 shows an example of the light-receiving characteristics of the light-receiving elements shown in FIGS. 3 to 5 above. The wavelength sensitivity curves shown by the dotted lines in the same figure are sequentially shown from the long wavelength side.
In _1-x3 Ga _x3 As _y3 P _1-y3 １９、In _1-x2 Ga _x2 As _y2 P _1-y2 １
8, In _1-x1 Ga _x1 As _y1 P _1-y1 17 and InP16, and as a whole can have wavelength sensitivity in an extremely wide range as shown by the solid line A. In addition, in the above embodiment, InP-
The example of In _1-x Ga _x As _y P _1-y was mentioned, but CdTe−
Of course, Hg _1-x Cd _x Te, GaAs-Al _1-x GaAs, etc. may also be used.

As shown above, the photodetecting element of the present invention does not require complicated procedures such as bonding multiple elements with different wavelength characteristics as in the past, and it is possible to fabricate a continuous series of epitaxial layers on a substrate. Not only can it be easily formed using a simple manufacturing method that is generally well known, including the layer growth process, photoetching, and electrode formation process, but it also has extremely high mechanical strength and is of great industrial value.

[Brief explanation of the drawing]

Figure 1 shows the relationship between the mixing ratio x of Hg _1-x Cd _x Te and the band gap (cutoff wavelength), Figure 2 a, b
3 is a perspective view showing a conventional multi-wavelength photodetecting element, FIGS. 3a, b, and c are diagrams showing a procedure for forming a multi-wavelength photodetecting element according to an embodiment of the present invention, and FIGS. 4 and 5 are A structural perspective view showing an improvement of the embodiment shown in FIG. 3, No. 6
The figure is a characteristic diagram showing multi-wavelength photosensitivity characteristics according to the present invention. 16-19... compound semiconductor, 24a-24
d, 25a to 25d...power supply, 26...separation groove.

Claims (1)

[Scope of Claims] 1. A semiconductor device comprising: a plurality of epitaxial layers grown on a substrate such that at least a portion of the surface of each layer is exposed; and an electrode formed on a portion of the exposed portion of the epitaxial layer. . A semiconductor light receiving device in which each exposed portion of each of the epitaxial layers has a predetermined wavelength sensitivity. 2. The semiconductor light receiving device according to claim 1, wherein the electrodes on the exposed portions of each epitaxial layer are electrically isolated from each other. 3. The semiconductor light receiving device according to claim 1, wherein the exposed portion of each epitaxial layer is electrically isolated by a groove.