Gamma ray detectors with HgCdTe contact layers

A new device structure for room-temperature gamma ray spectrometry has been developed and demonstrated. The device is a heterojunction p-i-n, HgCdTe/CdTe/HgCdTe structure. The p layer is Au doped with N/sub A/ = 1.9 x 1016 cm-3, μ/sub p/ = 35 cm2/Vs, and a Cd composition x/sub Cd/ = 0.6. The n layer is In doped with N/sub D/ = 2 x 1017 cm-3, μ/sub n/ = 1880 cm2/Vs, and x/sub Cd/ = 0.31. Ohmic contacts were achieved using electron beam evaporated Au (p layer contact) and In (n-layer contact). Devices (with approximately 2-mm2 area, 2-mm thickness) exhibited reverse leakage currents of 50 pA--4 nA, good photovoltaic response with visible light, and voltage breakdowns in excess of 1000 V. At 250-V reverse bias, the energy resolutions at the principal photopeaks of Am-241 (60 keV) and Co-57 (122 keV) were 12.5% and 8.4%, respectively