Takao Chikamura

The heterojunction ZnSe-(Zn1−xCdxTe)1−y(In2Te3)y having high sensitivity in the visible light range and its applications

Abstract The effect of a ZnSe film on the heterostructural ZnSe-(Zn 1− x Cd x Te) 1− y (In 2 Te 3 ) y film was studied from the standpoint of crystal growth. It is made clear that the ZnSe film improves the crystallinity of the Zn 1− x Cd x Te) 1− y (In 2 Te 3 ) y film evaporated on the ZnSe film and improves the spectral sensitivity of the heterostructure in the visible to the near-infrared light range. This heterostructure which consists of many elements can be fabricated by simple evaporation and anneal methods. One of the applications of this heterostructure is the photoconductive target in a camera tube. A camera tube with such a heterostructure is called “Newvicon” and has excellent features such as high sensitivity, low dark current, no burn-in and small lag. This heterostructure can be also applied to illuminometers photometers and solid state imagers.

Spectral response of ZnSe‐Zn1−xCdxTe heterojunction

The spectral response of ZnSe‐Zn1−xCdxTe (0⩽x⩽1) heterojunction is described. The heterojunction is formed by vacuum evaporation of ZnSe and Zn1−xCdxTe doped with In2Te3. The spectral response of this heterojunction is discussed for two cases, illuminated from the ZnSe side and from the Zn1−xCdxTe side. The theoretical results, based upon the assumption that the carriers excited by incident light are mainly transported by drift field, are in good agreement with the experimental results. Moreover, we could obtain a high internal quantum efficiency of 0.9 over the visible light range in this heterojunction.

Spectral response of boron‐implanted amorphous silicon Schottky diode

The spectral response of Schottky diodes on hydrogenated amorphous silicon implanted with boron has been investigated. The decrease in sensitivity in the short‐wavelength range has been observed in samples implanted with the boron dose of more than 1.6×1013 ions/cm2. The experimental spectral responses are in good agreement with theoretical responses derived from the assumption that the photoexcited carriers are mainly transported by drift field.

A CCD Imager Using ZnSe-Zn1-xCdxTe Heterojunction Photoconductor

A new CCD imager, having ZnSe-ZnCdTe heterojunction photoconductor as a photosensor which is vacuum-deposited on the CCD scanner, has been fabricated. The device has 404 (H) × 506 (V) scanning elements, each element measures 24 µm(H) by 14 µm(V), and the imaging area is 9.0 mm(H) × 6.7 mm(V) in size which is applicable to 2/3 inch camera format. The CCD scanner is fabricated with denuded zone which defines the defect-free device. A glass-reflow process is introduced to obtain the high breakdown of the heterojunction diode. The experimental result are as follows,; The sensitivity is 0. 16 µA/lx (3200 K). The horizontal and the vertical resolution are 280 and 450 TV lines, respectively. Dark current is 2 nA/cm2 for the photosensor (27°C). The signal to noise ratio is above 60 dB. The smearing suppression is effective for reducing the blooming phenomenon under the intense light illumination. The successful blooming suppression is achieved by this PLOSS structure device with metal screen grid. The high light exposure is allowable up to 1000 times as intense as the saturation exposure.