E. Belas | Searcharxiv

arXiv2020

Space charge formation in chromium compensated GaAs radiation detectors

Space charge formation in chromium-compensated GaAs sensors is investigated by the laser-induced 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 cm2/Vs. We developed and successfully applied theoretical model based on fast hole trapping in the system with spatially variable hole conductivity.

physics.app-ph↗

arXiv2010

Systematic investigation of influence of n-type doping on electron spin dephasing in CdTe

We used time-resolved Kerr rotation technique to study the electron spin coherence in a comprehensive set of bulk CdTe samples with various concentrations of electrons that were supplied by n-type doping. The electron spin coherence time of 40 ps was observed at temperature of 7 K in p-type CdTe and in n-type CdTe with a low concentration of electrons. The increase of the concentration of electrons leads to a substantial prolongation of the spin coherence time, which can be as long as 2.5 ns at 7 K in optimally doped samples, and to a modification of the g factor of electrons. The influence of the concentration of electrons is the most pronounced at low temperatures but it has a sizable effect also at room temperature. The optimal concentration of electrons to achieve the longest spin coherence time is 17-times higher in CdTe than in GaAs and the maximal low-temperature value of the spin coherence time in CdTe is 70 times shorter than the corresponding value in GaAs. Our data can help in cross-checking the predictions of various theoretical models that were suggested in literature as an explanation of the observed non-monotonous doping dependence of the electron spin coherence time in GaAs.

cond-mat.mtrl-sci↗