Space charge formation in chromium compensated GaAs radiation detectors

Abstract

Space charge formation in chromium-compensated GaAs sensors is investigated by the laserinduced transient current technique applying pulsed and DC bias. Formation of non-standard space charge manifested by an appearance of both negatively and positively charged regions in DC biased sensors was revealed during 5 ms after switching bias. Using Monte Carlo simulations of current transients we determined enhanced electron lifetime τ = 150 ns and electron drift mobility μd = 3650 cm 2 /Vs. We developed and successfully applied theoretical model based on fast hole trapping in the system with spatially variable hole conductivity.

Charge Transport and Space-Charge Formation in Cd1−xZnxTe1−ySey Radiation De

“…The sample is characterized using LTCT in combination with a pulsed bias, which allows us to suppress the space-charge formation and to study charge-trapping effects on the current waveforms, thus enabling easier evaluation of the electron-(hole-) drift-mobility carrier-trapping and -detrapping times [18,19]. Electron (hole) current waveforms are measured by illuminating a semitransparent cathode (anode) using a laser pulse with an above-band-gap wavelength at 660 nm, which is absorbed in less than 1 µm under the illuminated electrode [20].…”

“…The laser and bias pulse positions are synchronized as shown in Fig. 1 and characterized by a laser-pulse delay (LPD), bias pulse width (BPW), depolarization time (DT), and pulsing period (PP) [18]. The laser pulse width has a FWHM of about 2 ns.…”

“…Decreasing the LPD to the microsecond timescale, the space-charge formation induced by carrier injection or depletion induced by nonohmic contacts can be suppressed. This option simplifies the MC simulations, offering the possibility to directly determine the lifetime of drifting carriers from the slope of the current waveform (CWF) [18,22,23].…”