JPS63308971A - Photodetector - Google Patents

Abstract

PURPOSE:To select cut-off wavelength continuously at low cost by providing a means through which a substance which has first and second main surfaces, is brought into contact with a substrate on the first main surface and includes a large number of localized levels in a forbidden band is brought into contact with a substance having high conductivity on the second main surface, and voltage is applied between the substrate and the substance having high conductivity. CONSTITUTION:When amorphous silicon 2 is irradiated with infrared beams 8 having energy hupsilon, electrons 4 and holes 5 are generated. Holes having energy larger than an energy barrier phib shaped in the amorphous silicon 2 on the interface of a P-type single crystal silicon substrate 1 and the amorphous silicon 2 are discharged to the P-type single crystal silicon substrate 1 by a tunnel effect by an electric field, and changed into photocurrents (the arrow A). On the other hand, electrons 4 are discharged similarly to a metal 3 (the arrow B), and an empty localized level can be shaped. Cut-off wavelength lambdac is determined by the energy barrier phib, and phib is decided by the work function of the amorphous silicon 2. Accordingly, the energy barrier phib can also be selected within a wide range continuously, thus freely selecting cut-off wavelength lambdac.

Description

[Detailed description of the invention] [Industrial application field] The present invention is applicable to a photodetecting device.

[Prior Art] Fig. 4 is a cross-sectional structure of a conventional photodetecting device (a type of photodetecting device), and an operational diagram showing 3.
FIG. 5 is its energy band diagram. Look at the diagram,
1 is P-type medium crystal silicon, 4 is an electron, 5 is a hole, 6 is platinum silicide, and 8 is infrared light. Further, F represents the Fermi level, Φb represents the height of the Schottky barrier, and h represents the energy of light.

Next, the operation will be explained. FIG. 4 shows the structure of a Schottky barrier photodetecting device formed by a Schottky junction of P-type crystalline silicon 1 and platinum silicide 6. In FIG. Fifth
In the energy band diagram shown in the figure, infrared light 8 is applied to platinum silicide 6.
When is irradiated, electrons 4 and holes 5 are generated, and the holes 5 move randomly in the platinum silicide 6 until they recombine with electrons. During the movement, the platinum silicide 6 and the Schottky Among the holes 5 that have reached the junction interface, those whose energy is greater than the height Φb of the Schottky barrier are emitted from the platinum silicide 6 into the P-type antagonist silicon 1 and become a photocurrent. Here, the height Φb of the Schottky barrier is determined by the work function of platinum silicide 6. At this time, the cutoff wavelength λC of the photodetection gi position is determined by the height Φb of the Schottky barrier, and λC(μ
l1l)-1,24/Φb(eV).

[Problems to be solved by R-mei] Conventional photodetection devices are constructed as described above, but the use of platinum makes them expensive, and the work function of platinum silicide 6 increases the Schottky barrier. SaΦb
is determined, and the cutoff wavelength λC is determined, so there are problems such as the cutoff wavelength/IC cannot be freely selected.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a photodetecting device that is inexpensive and can continuously select cutoff wavelengths over a wide range.

Means for Solving Problem F] A photodetecting device according to the present invention has first and second main surfaces, the first main surface is in contact with a substrate, and a large number of localized units are detected in a forbidden state. The second main surface of the substrate is brought into contact with a highly conductive substance, and a voltage is applied between the substrate and the highly conductive substance.

[Operation 1] The photodetection device according to the present invention detects a substance having a first and second main surface and containing a large number of localized levels in a forbidden book.
Since it is constructed by applying a voltage between the substrate and the highly conductive material on each of the first and second main surfaces, avoiding contact with the substrate and the highly conductive material, it is inexpensive and can be used in prohibited locations. By changing the composition of a material containing a large number of localized levels, it is possible to continuously change the work function over a wide range. This makes it possible to continuously change the energy barrier that can be generated over a wide range, making it possible to freely select the cutoff wavelength.

Embodiment of the Invention] FIG. 1 is a schematic diagram showing a cross-sectional structure of an embodiment of the invention, and FIG. 2 is an energy band diagram thereof. In the figure, 1 is P-type medium crystalline silicon, 2 is amorphous silicon, 3 is a metal such as aluminum, 4 is an electron, 5 is a hole, 7 is a DC voltage, and 8 is infrared light. Further, Er represents the Fermi level, Φb represents the energy barrier, and hν represents the energy of light.

Next, the operation will be explained. In Fig. 1, an amorphous silicon 2 with a thickness of about 50 mm, which is an amorphous semiconductor containing many localized units, is brought into contact with a P-type crystalline silicon 1, and then a conductive material such as aluminum is added. high metal 3
2 is a cross-sectional view of a photodetecting device in which a metal 3 is brought into contact with amorphous silicon 2 and a DC voltage 7 is applied to the silicon substrate 1 so that a metal 3 has a positive potential. Note that an amorphous semiconductor containing many localized units can be obtained, for example, by depositing a silicon-based amorphous semiconductor using a plasma CVD method in a P6 atmosphere at 300° C. or higher. As shown in FIG. 2, since the amorphous silicon 2 has a high resistivity, the electric field is concentrated here. In addition, amorphous silicon 2 has many localized levels, but approximately the units below the Fermi level "r" are filled with electrons, and the units above are not filled with electrons.Here, amorphous silicon 2 When infrared light 8 of energy hν is illuminated by 1), electrons 4 and holes 5 are generated. Holes 5
Among them, at the interface between the P-type crystalline silicon substrate 1 and the amorphous silicon 2, the electric field waits for an energy greater than the energy barrier Φb formed in the amorphous silicon 2. A photocurrent is emitted to the child crystal silicon substrate 1 (arrow A). On the other hand, the first child 11 is released into the muscle V1 (arrow B), creating an empty localized level.

The cutoff wavelength λ0 in this case is determined by the energy barrier Φb, which is determined by the work function of the amorphous silicon 2, as in the conventional photo-detecting device. Silicon-based amorphous semiconductors such as amorphous silicon 2 can have their physical constants changed continuously over a wide range by changing the composition by, for example, adding germanium, nitrogen, or tin. and
Therefore, the energy barrier Φb is also 3! Since it can be systematically selected over a wide range, the cutoff wavelength λC can be freely selected.

In the above embodiment, P-type wheel crystal silicon 1 was used as the single-crystal semiconductor, but N-type single-crystal semiconductor may also be used. However, in this case, it is necessary to apply a DC voltage 7 such that the metal 3 has a negative potential with respect to the N-type single crystal semiconductor. Further, substances other than silicone may be used. Furthermore, in addition to amorphous silicon 2, which is an amorphous semiconductor as in the above example, the substance containing a large number of localized li1 levels in the forbidden band may also be a substance containing a large number of localized levels in the forbidden band. If available, polycrystalline semiconductors or insulators are fine.
Its thickness is 100 mm if the carrier is tunnelable.
0 A f! i! It can be thickened up to 4 degrees. On the other hand, if a highly conductive wire such as the metal 3 is made thin to several tens of amperes, it becomes possible to detect even light incident from the surface side of the metal 3, as shown in FIG.

[Effects of the Invention] As described above, according to the present invention, it has first and second main surfaces, and a large number of localized It! 1 including place
1J quality is brought into contact with the three plates and a highly conductive substance on each of the first and second main surfaces, and a voltage is applied between the substrate and the highly conductive substance, so it is inexpensive and Furthermore, it is possible to obtain a highly flexible photodetection device in which the cutoff wavelength can be continuously selected over a wide range.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing one embodiment of this invention, FIG. 2 is an energy band diagram thereof, FIG. 3 is a sectional view showing another embodiment of this invention, and FIG. 4 is a sectional view showing another embodiment of this invention. is a sectional view showing a conventional device, and FIG. 5 is an energy band diagram thereof. In the figure, 1 is P! ¥I A crystalline silicon, 2 is amorphous silicon, 3 is metal, 4 is electron, 5 is hole, 6 is platinum silicide, 7 is DC voltage, and 8 is infrared light. Note that the same reference numerals in each figure indicate the same or corresponding parts.

Claims (8)

[Claims] (1) A substance that has a substrate, first and second main surfaces, is in contact with the substrate at the first main surface, and includes a large number of localized levels in a forbidden band; A photodetector comprising a highly conductive substance in contact with a second main surface, and means for applying a voltage between the substrate and the highly conductive substance. (2) The photodetection device according to claim 1, wherein the substance containing a large number of localized levels in the forbidden band is an amorphous semiconductor. (3) The photodetecting device according to claim 2, wherein the amorphous semiconductor is amorphous silicon. (4) The photodetecting device according to any one of claims 1 to 3, wherein the substrate is a single crystal semiconductor. (5) The photodetecting device according to claim 4, wherein the single crystal semiconductor is single crystal silicon. (6) The photodetecting device according to any one of claims 1 to 5, wherein the highly conductive substance is a metal. (7) The photodetecting device according to claim 6, wherein the metal is aluminum. (8) The voltage creates an electric field in the forbidden band that is sufficient to cause electrons and holes generated in the material by incident light to be emitted toward the substrate or a highly conductive material, respectively, by a tunnel effect. 8. The photodetecting device according to claim 1, wherein the value is a value generated in a substance containing a large number of localized levels.