Investigation of the Recombination and Trapping Processes of Photoinjected Carriers in Semi-Insulating Cr-Doped GaAs Using PME and PC Methods

Abstract

Investigation of the recombination and trapping processes of photoinjected carriers in semi-insulating Cr-doped GaAs (ρ ∼ 108 Ω cm) has been made at 80 and 300°K, using the photomagnetoelectric (PME) and photoconductive (PC) effects under large-injection conditions. A generalized theory for the PME and PC effects is developed, taking into account the variation of carrier lifetimes with injected-carrier density (i.e., τn = κΔnβ) and of the trapping of holes in the Cr levels (i.e., Δp = ΓΔn, Γ<1), by using a simple recombination and trapping model. The result yields a power-law relationship between the PME short-circuit current and the photoconductance, in a form that IPME varies as ΔG2/(2+β), valid for different injection ranges. Two well-defined ranges of injection were observed from the present results: In region I (high injection), IPME is directly proportional to ΔG (i.e., β = 0), and in region II (intermediate injection), IPME varies with ΔG1.2 (i.e., β = −⅓). Numerical values of τn, τp, and IPME as functions of ΔG are given. The results are in good agreement with the theoretical predictions.

Optical Pump–Terahertz Probe Study of HR GaAs:Cr and SI GaAs:EL2 Structures with Long Charge Carrier Lifetimes

“…The results of Ref. [17] are better correlated with the OPTP data obtained for SI-GaAs [9]. As can be seen, there are considerable differences in the charge carrier lifetime values in GaAs obtained by OPTP and by the measurements of photoconductivity decay or charge collection efficiency.…”

“…To the best of our knowledge, OPTP spectroscopy has not previously been used to study GaAs:Cr. Nevertheless, the relaxation dynamics of charge carriers in GaAs:Cr were studied by measuring the photoluminescence decay, stationary photoconductivity and photoelectromagnetic effect [16,17]. In these studies, 60-600 ns [16] and 0.5-5 ns [17] lifetimes for electrons were obtained at relatively low injection levels.…”

“…Nevertheless, the relaxation dynamics of charge carriers in GaAs:Cr were studied by measuring the photoluminescence decay, stationary photoconductivity and photoelectromagnetic effect [16,17]. In these studies, 60-600 ns [16] and 0.5-5 ns [17] lifetimes for electrons were obtained at relatively low injection levels. The values obtained in [16] are in good agreement with the data obtained from the measurements of charge collection efficiency (approximately 80 ns [4]).…”

Impurity and Defect Behavior in High-Purity Epitaxial GaAs.

“…There will also be a heavier-doped region located at the surface due to surface states. GaAs, we will approximate its behavior with a single -75deep acceptor near midgap [74,75]. It is well-known, however, that its effects are somewhat more complicated than this model [73,76].…”