Abstract
Polycrystalline cadmium telluride (CdTe) X-ray photodetector with advanced performance was fabricated in a Schottky diode form by direct thermal deposition (evaporation) on pixelized complementary metal oxide semiconductor (CMOS) readout panel. Our CdTe X-ray detector shows such a variety of benefits as relatively low process temperature, low cost, low operation voltage less than 40 V, and higher sensitivity and spatial resolution than those of commercial a-Se detectors. CdTe has cubic Zinc Blende structure and maintains p-type conduction after growth in general. For low voltage operation, we succeeded in Cl doping at all stage of CdTe film deposition, and as a result, hole concentration of p-type CdTe was reduced to ~1012 cm−3 from ~1015 cm−3, and such concentration reduction could enable our Schottky diode with Ti electrode to operate at a reverse bias of less than 40 V. Our CdTe Schottky diode/CMOS pixel array as a direct conversion type imager demonstrates much higher resolution X-ray imaging in 7 × 9 cm2 large scale than that of CsI/CMOS array, an indirect conversion imager. To our limited knowledge, our results on polycrystalline CdTe Schottky diode/CMOS array would be very novel as a first demonstration of active pixel sensor system equipped with directly deposited large scale X-ray detector.
Highlights
Commercial direct type active matix X-ray imager consists of amorphous selenium (a-Se) photodetector and a-Si TFT switch in sensor system; the a-Se detector/a-Si TFT combination is classified www.nature.com/scientificreports/
Our results on polycrystalline cadmium telluride (CdTe) Schottky diode/CMOS array would be very novel as a first demonstration of active pixel sensor (APS) system equipped with directly deposited large scale X-ray detector. (According to Table S1, overall properties such as electron-hole pair creation energy (W) and mobility × carrier life time product in our polycrystalline CdTe material are shown and regarded quite desirable)
CdTe film growth on Ti appears successful as seen in Fig. 1d where Ti film pattern is added on Al pixel electrode
Summary
Silah Lee[1], Jin Sung Kim[1], Kyeong Rok Ko1, Gun Hwan Lee[2], Dong Jin Lee[3], Dong wook Kim[3], Jin Eui Kim[3], Ho Kyung Kim 4, Dong Woon Kim4 & Seongil Im1. Our CdTe Schottky diode/CMOS pixel array as a direct conversion type imager demonstrates much higher resolution X-ray imaging in 7 × 9 cm[2] large scale than that of CsI/CMOS array, an indirect conversion imager. Our results on polycrystalline CdTe Schottky diode/CMOS array would be very novel as a first demonstration of active pixel sensor system equipped with directly deposited large scale X-ray detector. Our CdTe Schottky diode/CMOS array demonstrates much higher resolution X-ray imaging in 7 × 9 cm[2] large scale as a direct conversion APS imager than that of CsI/CMOS array, an indirect conversion imager. Our results on polycrystalline CdTe Schottky diode/CMOS array would be very novel as a first demonstration of APS system equipped with directly deposited large scale X-ray detector. Our results on polycrystalline CdTe Schottky diode/CMOS array would be very novel as a first demonstration of APS system equipped with directly deposited large scale X-ray detector. (According to Table S1, overall properties such as electron-hole pair creation energy (W) and mobility × carrier life time product (μτ) in our polycrystalline CdTe material are shown and regarded quite desirable)
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