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

Abstract

The electron-and hole-transport properties in cadmium zinc telluride selenide (CZTS) crystals are studied using a laser-induced transient-current technique with pulsed and dc bias. The internal electric field profile and velocity of surface recombination are determined by Monte Carlo simulations of electron and hole transient currents combined with a numerical solution of the driftdiffusion equation coupled with Poisson's equation. Electron and hole drift mobilities of μe = 830 cm 2 /Vs and μh = 40 cm 2 /Vs, respectively, are determined. We also develop a simple technique for evaluating surface recombination directly from measured current waveforms without the need for numerical simulation. The good quality of the prepared detector at pulsed bias, with electron-and hole-mobility-lifetime products of (μτ)e = 1.9 × 10 −3 cm 2 /V and (μτ)h = 1.4 × 10 −4 cm 2 /V, respectively, are observed. The formation of a positive space charge, originating from hole injection combined with a recombination level, is found. We observe a significant position dependence of the lifetime of electrons and holes in dc bias due to hole injection. The experiment is successfully fitted by a simple model dominated by a single deep recombination level with an energy of Et = EC − 0.73 eV; concentration of 7.3 × 10 11 cm −3 ; and electron-and hole-capture cross sections of 3.5 × 10 −14 cm 2 and 6.5 × 10 −14 cm 2 , respectively.

Quaternary Semiconductor Cd1−xZnxTe1−ySey for High-Resolution, Room-Temperature Gamma-Ray Detection

“…bias in conjunction with Monte-Carlo simulation which turned out to be 830 and 40 cm 2 V −1 s −1 , respectively [60]. It can be noticed that the µτ product obtained by them were higher than that reported by Chaudhuri et al Ref.…”

“…The drift mobilities of the electron and holes were calculated to be 692 and 55 cm 2 V −1 s −1 , respectively. As mentioned above, Pipek et al measured the electron and hole mobilities using a laser-induced transient-current technique with pulsed and dc bias in conjunction with Monte-Carlo simulation which turned out to be 830 and 40 cm 2 V −1 s −1 , respectively [60]. It can be noticed that the µτ product obtained by them were higher than that reported by Chaudhuri et al Ref.…”

“…In their most recent report, Roy et al reported the electron µτ product to be in the range 4.0-6.5 × 10 −3 cm 2 V −1 . Pipek et al measured the mobilities and lifetimes of both electrons and holes using a slightly different approach in THM grown CZTS ([Se] = 2 at%) detectors with a resistivity of 1.1 × 10 10 Ω-cm [60]. They used the laser-induced transient-current technique with pulsed and dc bias in conjunction with Monte-Carlo simulation-based calculations for the transport properties studies.…”

“…They also observed that the presence of hole traps indirectly enhances the µτ product of electrons. Pipek et al measured the transients related to the electron-and hole-current triggered by pulsed and dc biases in a CZTS detector using a laser induced transient current technique in conjunction with numerical simulations [60]. They reported one shallow electron and one shallow hole trap center, and a strong recombination center located at 0.73 eV below the conduction band edge.…”