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

We report on the growth of very thick (>260 μm) 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 μm/h to 70 μm/h. A heterojunction diode was fabricated by growing a 90-μm-thick CdTe layer on an n+-Si substrate, which exhibited good rectifying behavior and had a low reverse bias leakage current of 0.18 μA/cm2 at 100 V bias. The diode clearly demonstrated its gamma radiation detection capability by resolving energy peaks from the 241Am radioisotope during room-temperature measurements. By cooling the diode detector to −30°C, the leakage current could be reduced by three orders of magnitude from the room-temperature value. At this operating condition dramatic improvements in the pulse height spectrum were observed.