High-temperature operation of a radiation detector made of a type IIa diamond single crystal synthesized by a HP/HT method

Characteristics of a synthetic diamond radiation detector in high-temperature environments up to 196°C were investigated. The radiation detector was made of a high-purity type IIa diamond single crystal synthesized by a high-pressure and high-temperature (HP/HT) method. In order to suppress a strong increase in leakage current in a high-temperature environment, a surface barrier structure composed of Schottky and ohmic contacts was adopted. The detector operated as an energy spectrometer for 5.486 MeV α particles up to 156°C. The peak due to the α particles obtained at 68°C slightly shifted to the higher-energy side compared with the same peak obtained at 25°C; furthermore, the energy resolution of these peaks was improved with the increase in the detector temperature. Effects of trapping and detrapping on holes were suppressed by thermal excitation, and this resulted in an improvement in collection efficiency of charge carriers. With a further increase in the detector temperature, loss of charge carriers became more significant. Finally, operation of the detector was prevented at 196°C by a polarization phenomenon caused by accumulation of space charge in the detector.