Characterization of CdTe/n$^{+}$ -Si Heterojunction Diodes for Nuclear Radiation 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 $\mu$ m thick n-type CdTe buffer layer on the n $^{+}$-Si substrate, followed by the growth of 100 $\mu$m thick undoped p-CdTe layer. The diode fabricated showed very good rectification property with a low value of the reverse bias leakage current, typically $1.26 \times 10^{- 7}$ A/cm $^{2}$ for an applied reverse bias of 60 V. The diode clearly demonstrated the gamma radiation detection capability by resolving energy peaks from the $^{241}$Am radioisotope during the radiation detection test performed at room temperature.