A CdTe/n ϩ -GaAs heterojunction diode for a room-temperature nuclear radiation detector has been developed and demonstrated. The heterojunction diode was fabricated by growing a 2-5-µm-thick iodine-doped n-CdTe buffer layer on the n ϩ -GaAs substrates, followed by about 100-µm-thick undoped p-like single crystalline CdTe layer using metalorganic vapor-phase epitaxy. The n-type buffer layer was found to be essential to improve the junction property of the diode detector. The diode detectors exhibited good rectification property and had the reverse leakage currents typically from 1 µA/cm 2 to 5 µA/cm 2 at 40 V bias. The detector clearly demonstrated its energy resolution capability by resolving the 59.54-keV gamma peak from the 241 Am radioisotope during the radiation detection test.

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