In this work we present the results of experimental study of the current-voltage characteristics, the electric field distribution and the charge collection efficiency in X-ray sensors based on high resistivity, chromium compensated gallium arsenide (HR GaAs). The experimental samples were 0.1-0.25 cm² pad sensors with the sensitive layer thickness in the range of 250-1000 μm. It has been shown that the current-voltage characteristics in the range 0.02 – 1 V are determined by the high-resistance sensor bulk. A physical model of the nonequilibrium charge carrier transport has been suggested to estimate the Schottky barrier height in the contact of “metal-semiconductor” and the sensor material resistivity. It has been established that the sensor resistivity reaches 1.5 GOhm⋅cm at room temperature, with the Schottky barrier height constituting 0.80 – 0.82 eV. The electric field distribution was investigated using the Pockels effect at a wavelength of 920 nm. It has been found experimentally that in HR GaAs sensors the electric field distribution is much more homogeneous compared to the sensors based on SI GaAs: EL2. It has been shown that the temporal fluctuations of the electric field are absent in HR GaAs sensors. Analysis of the charge collection efficiency as a function of bias has demonstrated, that in the HR GaAs material the values of the mobility-lifetime product of the nonequilibrium charge carriers are in the order of 10^-4 cm2/V and 3⋅10^-7 cm2/V for electrons and holes, respectively.

Date Published: 5 September 2014
PDF: 12 pages
Proc. SPIE 9213, Hard X-Ray, Gamma-Ray, and Neutron Detector Physics XVI, 92130G (5 September 2014); doi: 10.1117/12.2061302

Published in SPIE Proceedings Vol. 9213:
Hard X-Ray, Gamma-Ray, and Neutron Detector Physics XVI
Arnold Burger; Larry Franks; Ralph B. James; Michael Fiederle, Editor(s)