5 September 2014 Investigation of the current-voltage characteristics, the electric field distribution and the charge collection efficiency in x-ray sensors based on chromium compensated gallium arsenide
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Abstract
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.
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A. Tyazhev, V. Novikov, O. Tolbanov, A. Zarubin, M. Fiederle, E. Hamann, "Investigation of the current-voltage characteristics, the electric field distribution and the charge collection efficiency in x-ray sensors based on chromium compensated gallium arsenide", Proc. SPIE 9213, Hard X-Ray, Gamma-Ray, and Neutron Detector Physics XVI, 92130G (5 September 2014); doi: 10.1117/12.2061302; https://doi.org/10.1117/12.2061302
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