The investigation of semi-insulating gallium arsenide bulk material for use in room temperature charged particle and gamma ray spectroscopy.

Abstract

Bulk semi-insulating GaAs grown by the liquid encapsulated Czochralski (LEC) method has been investigated as a possible room temperature charged particle and gamma ray spectrometer. Pulse height spectra measured from a 5.5 MeV alpha particle source demonstrated energy resolution ranging from 2.1% to 3.1% for several detectors with a typical resolution of 2.5%. Low energy gamma rays measured under room temperature operating conditions resulted in observed full energy peaks for 60 keV and 122 keV photons with measured FWHM's of 22 keV and 40 keV, respectively. Pulse height analysis utilizing different alpha particle sources and high energy X-rays disclosed non-uniform electric field distributions with widths that deviate strongly from $\sqrt{V}$ behavior. Consequences concerning the presence of deep level native defects in the bulk material are presented, including proposed models describing the effect of deep level ionization on the electric field distribution in the detector bulk. It is concluded that practical high resolution gamma ray detectors will require considerable material improvements over bulk LEC GaAs that is presently available.