Development of bulk semi-insulating GaAs semiconductor radiation detector at room temperature

A room temperature semiconductor based radiation detector is the most promising for an ionizing detector in the field of nuclear material control and accounting. GaAs is a wide band gap semiconductor with 1.42-eV at room temperature. The major aim of this study is to develop an alpha photoconduction detector which will be applied to nuclear power plants and nuclear material storage facilities. We designed and fabricated a bulk single crystal GaAs photoconducting detector by using an undoped semi-insulating wafer with a (100) orientation. The active area of the GaAs SI bulk detector was 10/spl times/10 mm with a 350 micron thickness. The GaAs sensor was prepared using the standard processes. Metal contacts on the surfaces were fabricated by using a thermal evaporator in vacuum condition. Ohmic contacts were fabricated at each side with Au at front side and Ni at rear. The leakage current response according to biased voltage was measured with a high precision electrometer. Alpha response was measured by a Pu-238 source with 5.5-MeV at room temperature and a 1-atm air condition. Pulse height spectra were obtained by standard electronics which consists of a preamplifier, a shaping amplifier, and a multi-channel analyzer. Alpha radiation was confirmed by using a thin metal plate which is sufficient enough to stop alpha particles. As a result the bulk GaAs SI detector was showed a good response for the alpha-radiation and is promising candidate for an alpha detector in an air condition.