Characterization of CdTe/n+-Si Heterojunction Diodes for Nuclear Radiation Imaging Detectors

CdTe/n⁺-Si heterojunction diodes were fabricated and characterized for the development of gamma ray detectors. With the careful control of the growth parameters thick single crystal CdTe epilayers of high-crystalline quality were grown directly on the (211) Si substrates in a metalorganic vapor phase epitaxy. The heterojunction diode was fabricated by growing a 5 mum thick n-type CdTe buffer layer on the n⁺-Si substrate, followed by the 100 mum thick undoped p-CdTe layer growth. The diode fabricated showed very good rectification property with a low value of the reverse bias leakage current, typically 1.2 times 10^-7 A/cm² for an applied reverse bias of 50V. The diode clearly demonstrated its gamma radiation detection capability by resolving energy peaks from the ²⁴¹Am radioisotope during the radiation detection test performed at room temperature.