Characterization of CdTe, CdxZn1−xTe and GaAs detectors

We report space-and-time current spectroscopy for characterization of high-quality GaAs thin films grown on semi-insulating gallium arsenide substrates. The approach is based on illumination of semiconductor material with an oscillating interference pattern formed of two light waves, one of which is phase modulated with frequency ω. The non-steady-state photocurrent flowing through the short-circuited semiconductor is the measurable quantity in this technique. The alternating current resulted from the periodic relative shifts of the photoconductivity and space charge electric field gratings arising in the crystal's volume under illumination. The results of measurements of semiconductor material's parameters of CdTe and CdxZn1−xTe detectors are presented. The experiments are carried out for the diffusion regime of signal excitation at light wavelength λ=1.15 μm. The sign, conductivity and diffusion length are estimated from the dependencies of the signal on the temporal and spatial frequencies. The high-quality GaAs thin films grown on semi-insulating gallium arsenide substrates are characterized. The experiments are carried out in the geometry of the Michelson interferometer at the illumination wavelength of 532 nm. The dependence of the non-steady-state photocurrent on spatial frequency of the interference pattern is measured, allowing estimation of the diffusion length of photoelectrons in GaAs thin film LD=40 μm.