JPS6113396B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a method for manufacturing a CdSe photoconductive film.

Since the CdSe photoconductive film has a large number of defects in the material, which are formed by donor levels created by Se vacancies, the dark current (Id) is relatively large and the ratio of the bright current (Ip) to the bright current (Ip) is Ip/Id.
is 4 to 5 digits at most. In addition, Id has severe temperature dependence, and when the temperature reaches 80°C, Ip/Id decreases to about three digits. Therefore, it cannot be applied to photoelectric conversion devices that require a large change in resistance value.

Te is used to fill the Se vacancies in this CdSe photoconductive film.
The dimensions are such that . Methods for adding Te include co-evaporation of CdSe-Te, CdSe
Vapor deposition with -CdTe mixtures is already known.
The former method is difficult to control the vapor pressure of Te, and the latter method has a constant mixing ratio, which is disadvantageous when changing the parameters of the photoconductive film.

The purpose of the present invention is to eliminate such drawbacks, and the purpose is to prepare CdSe and CdTe as separate deposition sources and set the deposition rate of CdSe to V _CS .
When the evaporation rate of CdTe is V _CT , the evaporation rate ratio R (R=V _CT /V _CS +V _CT ) of CdTe to the overall evaporation rate (V _CS +V _CT ) satisfies 0<R≦0.5. This is accomplished by a method of manufacturing a photoconductive film that includes vapor deposition.

Hereinafter, the present invention will be explained in detail based on examples. The method of the present invention is as shown in Figure 1.
In this method, CdSe1 and CdTe2 are prepared in separate evaporation ports 3 and 4, and the amount of evaporation is controlled to form a photoconductive film on the substrate 5. The basic idea at that time was
This is because it has been found that there is almost no difference in evaporation rate between CdSe and CdTe, and that a CdSe photoconductive film can be formed with good controllability by controlling the evaporation rate of each evaporation source. The results are shown in FIGS. 2 and 3.

The vapor deposition ports 3 and 4 are made of metal such as tungsten or molybdenum, and are configured to allow heating current to flow through each port independently. This current generates heat in the port, causing CdSe and CdTe to evaporate. Therefore, by changing the current flowing through each port, the amount of evaporation of CdSe and CdTe can be controlled independently. Tungsten and molybdenum ports
Since it does not react with CdSe or CdTe, it can be used any number of times and has good control reproducibility.

Note that the measurement of the deposition rate is, for example, for CdSe and CdTe.
This is carried out by a known method of taking the time differential of the evaporation amount using film thickness monitors prepared independently for each case.

FIG. 2 is a diagram showing changes in the bright current IP (A) and the ratio Ip/Id between the bright current IP and the dark current Id with respect to the ratio R of the evaporation rate. Here, the evaporation rate ratio R is expressed by the following equation.

R=V _CT /V _CS +V _CT , where V _CS ; evaporation rate of CdSe; V _CT ; CdTe
evaporation rate.

In the figure, curve 6 shows the change in Ip, and curve 7 shows Ip/Id
shows the change in Further, Δ indicates Ip/Id, and ● indicates Ip.

The conditions during vapor deposition were a substrate temperature of 270°C, and a CdSe
The evaporation rate V _CS is the frequency of the crystal oscillator per minute.
The value was set such that it changes by 3.5KHz.

In addition, the measurement conditions for Ip and Id are that the applied voltage is 6V,
The amount of light to be irradiated was set to 1000 lux.

FIG. 3 shows the variation of the rise time r ₉₀ and fall time d ₁₀ of the bright current Ip with respect to the ratio R of the evaporation rate.

In the figure, curve 8 shows the rise time, and curve 9 shows the fall time. The unit of time is (m sec).

Here, the rise time r ₉₀ is the time when the bright current Ip reaches 90% from the time t ₀ of light irradiation, as shown in Figure 4.
The fall time _R10 is _{the period from time t2 when} light irradiation is stopped to time _t3 when the bright current Ip reaches 10%.

According to this experiment, when the evaporation rate of each material is changed so that R is in the range of 0<R≦0.5, R
= 0 (without CdTe evaporation)
Ip/Id has improved by more than one order of magnitude (two orders of magnitude at the optimal point), and r ₉₀ and R ₁₀ have become smaller, increasing speed. The bright current Ip is almost constant up to R=0.2, but decreases rapidly when R≧0.2. At the same time, the response times r ₉₀ and d ₁₀ become faster. Therefore, by changing the evaporation rate ratio R, it is possible to obtain a photoconductive film with different properties depending on the purpose. This point is superior to the method of forming CdSe-CdTe by evaporating it from a single evaporation source.

[Brief explanation of the drawing]

FIG. 1 is a diagram for explaining the manufacturing method according to the present invention, and FIG. 2 is a diagram for explaining the manufacturing method according to the present invention.
Figure 3 shows changes in the rise time and fall time with respect to the evaporation rate ratio R; Figure 4 shows the rise time and fall time. FIG. 3 is a diagram for explaining time. In the figure, 1 is CdSe, 2 is CdTe, 3 and 4 are vapor deposition ports, and 5 is a substrate.

Claims (1)

[Claims] 1 CdSe and CdTe are prepared as separate evaporation sources,
The evaporation rate of CdSe is Vcs, and the evaporation rate of CdTe is V
When _CT is the evaporation rate of CdTe relative to the overall evaporation rate (V _CS +V _CT ), the ratio R of V _CT (R=V _CT /V _CS +V _CT ) is 0<R≦0.5. A method of manufacturing a photoconductive film comprising vapor deposition.