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 NA=1.9×1016 cm−3, μp=35 cm2/Vs, and a Cd composition xCd=0.6. The n layer is In doped with ND=2×1017 cm−3, μn=1880 cm2/Vs, and xCd=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.