Fabrication and Characterization of MOVPE-Grown CdTe-on-Si Heterojunction Diode-Type Gamma-Ray Detectors

Abstract

We report on the growth of very thick (>260 lm) high-crystalline-quality single-crystal CdTe epitaxial films on (211) Si substrates in a metalorganic vapor-phase epitaxy reactor, and the development of gamma ray detectors and their radiation detection properties. Films were grown with a high growth rate varying from 40 lm/h to 70 lm/h. A heterojunction diode was fabricated by growing a 90-lm-thick CdTe layer on an n + -Si substrate, which exhibited good rectifying behavior and had a low reverse bias leakage current of 0.18 lA/cm 2 at 100 V bias. The diode clearly demonstrated its gamma radiation detection capability by resolving energy peaks from the 241 Am radioisotope during roomtemperature measurements. By cooling the diode detector to -30°C, the leakage current could be reduced by three orders of magnitude from the roomtemperature value. At this operating condition dramatic improvements in the pulse height spectrum were observed.

Electrical Properties of Halogen-Doped CdTe Layers on Si Substrates Grown by Metalorganic Vapor-Phase Epitaxy

“…[1][2][3][4] We have previously reported on metalorganic vaporphase epitaxy (MOVPE) growth of thick singlecrystal CdTe layers (100 lm to 260 lm) on Si as well as on GaAs substrates and the development of gamma-ray detectors using these epilayers. 1,[4][5][6] The detectors were fabricated in a p-CdTe/n-CdTe/n + -Si heterojunction diode structure, where the p-CdTe and the n-CdTe layers were typically 100 lm and 5 lm thick, respectively. 5 The detectors were capable of detecting gamma radiation and measuring its energy distribution, when operated in pulse mode by applying a reverse bias voltage.…”

“…1,[4][5][6] The detectors were fabricated in a p-CdTe/n-CdTe/n + -Si heterojunction diode structure, where the p-CdTe and the n-CdTe layers were typically 100 lm and 5 lm thick, respectively. 5 The detectors were capable of detecting gamma radiation and measuring its energy distribution, when operated in pulse mode by applying a reverse bias voltage. However, the detector dark current was a major source of electronic noise, which increased with the applied reverse bias.…”