Room-Temperature Particle Detectors Based on Purified InP Single-Crystals Converted to Semi Insulating State by Annealing

Abstract

InP were grown by Czochralski technique. They were purified by admixture of Ta into the growth melt and then converted to semi-insulating state by annealing. Temperature dependent Hall measurements were carried out in the range from 300 K to 430 K and the activation energy of the impurity responsible for the semi-insulating state was determined from the slope of the straight line as 0.75 eV from the conduction band edge. This energy is much different from the activation energy of Fe2+ in InP, 0.65 eV, which was observed in the annealed InP grown with Fe admixture. InP wafer selected for fabrication of prototype particle detectors was lapped and chemo-mechanically polished on the both sides to final thickness of 0.25 mm. The detectors were fabricated by metal deposition of circular electrodes of 1 mm diameter overlaying on both sides of the wafer, using vacuum evaporation of Ni/Ge/Au. Detection performance of particle detectors was measured at room temperature by pulse-height spectra with alpha particles emitted from 241Am. Maximum of the spectral line corresponded to 85% of charge collection efficiency when 100 V voltage was applied