JPS6188571A - Photodetector - Google Patents

Abstract

PURPOSE:To improve sensitivity on the short wavelength side by making an N type dopant in concentration sufficient for increasing the mutau (the product of mobility and lift) of electrons on beam projection to contain into an amorphous semiconductor. CONSTITUTION:When P type a-Si:H in 120Angstrom , substantially intrinsic a-Si:H in 5,000Angstrom and Si:H in 500Angstrom containing N type crystallites are deposited on a glass/SnO2 substrate and intrinsic a-Si:H is shaped by a photodetector on which an Al electrode is evaporated, N2 gas is doped by 10ppm, 40ppm, 100ppm and 400ppm to SiH4. Accordingly, sensitivity on the long wavelength side slightly lowers with the increases of the quantity of N2 doped, but sensitivity on the short wavelength side is enhanced remarkably.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a photodetection device.

[Prior Art] Photodetection devices such as thick batteries and photodetectors have been used in the past. These photodetecting devices are devices that convert light into electrical energy, and since the fundamental structure and operating principle of the main parts are substantially the same, in the following description, for convenience, solar cells will be mainly explained.

Light incident on a solar cell and absorbed by the active region of the semiconductor generates holes and electrons, which are separated by an internal electric field and produce a current known as photocurrent and a photovoltage. A known voltage develops. Electrons flow toward the semiconductor region exhibiting n-type conductivity, and holes flow toward the semiconductor region or metal layer exhibiting the opposite conductivity.

A basic type of hydrogenated amorphous silicon solar cell with an intrinsic or undoped region is described in U.S. Pat. No. 406
It is disclosed in the specification of No. 4521.

Regarding hydrogenated amorphous silicon solar cells in which halogen is added to the undoped region, see Japanese Patent Application Laid-open No.
It is disclosed in Japanese Patent No. 42693.

The above undoped hydrogenated amorphous silicon semiconductor has approximately 25
When manufactured at the optimum substrate temperature of 0 to 350°C, only n
When irradiated with light, the slight n-type characteristics of this undoped hydrogenated amorphous silicon semiconductor act as donor-like defects in the intrinsic hydrogenated amorphous silicon semiconductor region. It is believed that if the undoped hydrogenated amorphous silicon semiconductor region is made to be substantially neutral rather than slightly n-type, the space charge region of an amorphous silicon solar cell having this region will increase. Based on this idea, in Japanese Patent Publication No. 59-29157, an attempt was made to compensate the undoped hydrogenated amorphous silicon semiconductor region with an n-type dopant to make it substantially neutral, thereby increasing the space charge layer. ing.

[Problems to be Solved by the Invention] In a photodetector, if the undoped hydrogenated amorphous silicon semiconductor slightly becomes n-type, which is compensated for with an n-type dopant to increase the space charge region, electron In the case of a photodetector in which the travel distance is long and the light incident side is an n-type semiconductor or metal barrier side, the electron mobility (μ) and the lifetime (
τ), the product μτ becomes relatively smaller than the hole μτ,
The present inventors have discovered that the sensitivity on the short wavelength side is significantly reduced, and when the light incident side is an n-type semiconductor, the sensitivity on the long wavelength side is reduced. .

The present invention has been made to solve these drawbacks.

[Means for Solving the Problems] The present invention provides a photodetection device that includes a substantially intrinsic amorphous semiconductor and has a potential barrier, in which a concentration of n that increases μτ of electrons during light irradiation is used. The present invention relates to a photodetection device characterized in that the amorphous semiconductor contains a type dopant.

[Practical example] In the present invention, a photodetecting device including a substantially intrinsic amorphous semiconductor and having a potential barrier is a hetero or homo p
A photodetection device such as an in-type, Schottky type, HIS type, or multi-junction type (pin/pin/pin, etc.), which is a substantially intrinsic semiconductor, i.e., a-8
i:H, a-Si:F:H, a-3iGe:H, a-3
Contains semiconductors such as iGe:F:H and a-3iSn:H, and has potential barriers that connect electrodes and semiconductors, semiconductors with different conductivity types, or metals or oxide films. It refers to a photodetector.

The substantially intrinsic amorphous semiconductor is, for example, a substantially intrinsic amorphous semiconductor containing silicon, and specific examples thereof include Si and 5iGe.

Examples include, but are not limited to, semiconductors made of SiC, 5iSn1Sin, etc., and compensated with at least one type of halogen atom such as a hydrogen atom or a fluorine atom. In addition, since it is used in a photodetector, its thickness is preferably 100 to 20,000 from the viewpoint of photocurrent, and more preferably 500 to 20,000.

In the present invention, the substantially intrinsic semiconductor is doped with a 9 degree n-type dopant that increases μτ of electrons upon irradiation with light.

Specific examples of the n-type dopant include N, P, AS, etc., and usually NH3, NF3, phosphine, A
When a semiconductor is deposited by a glow discharge decomposition method using sH3 or the like, it is doped by being deposited together with the semiconductor.

The preferred concentration of the n-type dopant in the semiconductor is n
Although it varies depending on the type dopant and the type of semiconductor, the number of atoms is generally 1014 to 1018/cm3, preferably 1015.
~5X 10"/cm". The number of atoms is 10
When the value is less than 1018/cm', the effect tends to disappear, and when it exceeds 1018/α3, the number of defects increases, so the μτ of holes decreases, and the absolute sensitivity tends to decrease significantly. It tends to become difficult to increase μτ of electrons during light irradiation and increase sensitivity on the short wavelength side, which is the objective of the present invention.

Doping with an n-type dopant may be done uniformly throughout the substantially intrinsic semiconductor. However, if the light is incident on the p-type semiconductor, the metal or oxide conductive film that creates the potential barrier, the side opposite to the light incidence is from the p-type semiconductor interface, the metal or oxide conductive film that creates the potential barrier. It is preferable to form the layer so that the concentration of the n-type dopant gradually decreases from about 1017 to 10"/cm', for example, from the viewpoint of not reducing the sensitivity on the long wavelength side.
When uniformly doping with an n-type dopant, it is preferable to dope to a thickness within about 2,000 layers, preferably 1,500 layers from the interface for the same reason.

Similarly, when the light incidence is reversed, the concentration of the n-type dopant decreases from the interface of the p-type semiconductor and the metal or oxide conductive film that forms the potential barrier toward the light incidence side. Preferably, only 2000 layers from the interface are doped with an n-type dopant.

As explained above, a photodetector having a potential barrier is constructed using a substantially intrinsic amorphous semiconductor doped with an n-type dopant at a concentration that increases the μτ of electrons when irradiated with light. Once manufactured, the resulting photodetector device may e.g.
When light enters from the p side in the case of in-type, or from the scrap metal side in the case of old S-type and Schottky types, μτ becomes large, so as shown in Figure 1, it is approximately 550n
Sensitivity below m increases significantly. As a result, the current value for short wavelength light such as fluorescent octopus increases by 1.5 to 2 times that in the case without doping.

Next, the photodetecting device of the present invention will be explained based on examples.

Actual Lt 5 Examples 1 to 4 and Comparative Example 1 P-type a was formed on a glass/5n02 substrate at a substrate temperature of 200°C.
-3i:H (Eg=2.05eV, σa=10-
6 (-〇・cm)) 120 people, essentially a-3i
:H(Eg=1.8eV 1△E=0.8eV, (
rd= 3 x 10 (Ω・cm)-1)500
0 people, Si:H containing n-type microcrystals (ΔE = 0.05e
V.

+7 (1 = 5 X-10-'(Ω・cu)-' )
After depositing 112 gas at 500 nm and using a photodetector with an N electrode to form a film of intrinsic a-3i:H, 112 gas was
= 10ppm for 84 140ppm, 100
11 pills and 400 pD were doped (corresponding to Examples 1 to 4, respectively), and the collection efficiency was compared with the case without doping (Comparative Example 1). The results are shown in Figure 1.

As can be seen from Table 1, as the amount of N2 doping increases, the long wavelength sensitivity slightly decreases, but it can be seen that the sensitivity of the layer wavelength measurement is significantly improved.

To see the effect in a concrete example, v- at fluorescence 12001ux
1 characteristic was investigated. Also, μ of one layer of electrons using the time-or-flight method. τ. was measured. The results are shown in Table 1.

[Margin below] As shown in Table 1, it can be seen that doping with N2 significantly improves the characteristics. Also μ of ill electron. τ.

It can be seen that the value becomes larger due to t12 doping.

. It was found in 5INS that the actual amount incorporated into the mold by N2 doping was about 1 mol%.

[Effects of the Invention] When the photodetection device of the present invention is used, the spectral sensitivity on the short wavelength side is significantly improved, and this has favorable characteristics as a sensor used in the visible region.

Also, when used as a solar cell in environments with a lot of visible light, such as fluorescent lights, it can generate a large amount of current, making it extremely effective as a power source for consumer devices (calculators, watches, etc.).

[Brief explanation of the drawing]

FIG. 1 shows the wavelength dependence of photocurrent at O bias of the photodetectors obtained in Examples 1 to 4 and the photodetector obtained in Comparative Example 1, which are implementation frames of the photodetection measure of the present invention. This is a graph showing the relative sensitivity with the number of photons held constant. ;1'1 figure wavelength (mm)

Claims (1)

[Scope of Claims] 1. In a photodetecting device that includes a substantially intrinsic amorphous semiconductor and has a potential barrier, an n-type dopant is added to the amorphous at a concentration that increases μτ of electrons during light irradiation. 1. A photodetecting device characterized in that the photodetecting device is contained in a quality semiconductor. 2. The photodetection device according to claim 1, wherein the photodetection device is a pin type, HIS type, or Schottky type device. 3 Substantially intrinsic amorphous semiconductors include Si, SiGe,
2. The photodetecting device according to claim 1, which is a semiconductor made of SiC, SiN, or SiSn and compensated with at least one of hydrogen atoms and halogen atoms. 4. The photodetecting device according to claim 1, wherein the n-type dopant is N, P or As. 5 The concentration of n-type dopant is 10^1^4 to 10 in number of atoms.
^1^3/cm^3 The photodetecting device according to claim 1. 6. The photodetecting device according to claim 1, wherein the concentration of the n-type dopant decreases from the p-type semiconductor interface or the oxide conductive film interface. 7 Up to 2 points from the p-type semiconductor interface or oxide conductive film interface
7. The photodetector device of claim 6, which is doped with an n-type dopant to a thickness of 0.000 Å. 8. Claims 1, 2, 3, 4, 5, 6 or 8, wherein the light is incident on the p-type semiconductor, metal or oxide conductive film side that forms a potential barrier. The photodetection device according to item 7. 9. Claims 1, 2, 3, 4, 5, and 6, in which the side opposite to the light incidence is a p-type semiconductor, a metal or oxide conductive film forming a potential barrier. Section or 7th
The photodetection device described in Section 1.