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Title:Photoluminescence studies of hydrogenation and other defect-related processes in III-V compound semiconductors
Author(s):Szafranek, Igor
Doctoral Committee Chair(s):Stillman, Gregory E.
Department / Program:Materials Science and Engineering
Discipline:Materials Engineering
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Engineering, Electronics and Electrical
Physics, Condensed Matter
Engineering, Materials Science
Abstract:Photoluminescence (PL) studies of defect-related processes in high-purity GaAs and related III-V compounds, are reported. A new effect of light-induced reactivation (LIR) or acceptors in p-type hydrogenated GaAs has been observed. This process is virtually athermal for weakly passivated acceptors such as Mg. Reactivation is persistent at cryogenic temperatures, but the material relaxes back to the passivated state at about room temperature. The LIR dependence on photon energy, illumination intensity, sample temperature and chemical identity of the passivated acceptor species indicates that LIR is electronically stimulated via recombination-enhanced vibrational excitation of acceptor-hydrogen complexes. A kinetic model that agrees with experimental data is proposed.
A shallow defect, labeled "A," that gives rise to the characteristic g(d,X) defect-bound exciton peak at 1.511$\sb2$ eV in GaAs grown by molecular beam epitaxy (MBE), has been investigated. This defect is acceptor-like, with the activation energy of about 24.8 meV, $\sim$1.7 meV less than that of C$\sb{\rm As}$ acceptors. Incorporation of the "A" defect as a function of MBE growth parameters has been studied, resulting in a successful growth of nearly defect-free GaAs over a wide range of deposition rates ($<$1 - $\sim$5 $\mu$m/h) under marginally As-stabilized surface conditions. Anomalous luminescence effects induced by the "A" defect have been observed and analyzed. Specifically, the defect causes an almost complete quenching of donor-bound excitions, which was frequently misinterpreted in the past as being due to extremely low donor concentration and compensation ratio in MBE-grown p-type GaAs.
The first quantitative study of layer intermixing in heavily Group IV(C$\sb{\rm As}$)-doped p-type Al$\sb{\rm x}$Ga$\sb{\rm 1-x}$As/GaAs superlattices has been performed for different annealing conditions. An enhancement of Al-Ga interdiffusion coefficients (D$\sb{\rm Al-Ga}$) in C-doped compared to intrinsic crystals has been observed, but significantly less than predicted by the charged point-defect (Fermi-level-effect) model. Also, contrary to the model, D$\sb{\rm Al-Ga}$ increases with increasing As$\sb4$ pressure in the annealing ampoule. Finally, dopant species dependence of the layer disordering in p-type superlattices, that is not accounted for by the model, has been observed.
Issue Date:1990
Rights Information:Copyright 1990 Szafranek, Igor
Date Available in IDEALS:2011-05-07
Identifier in Online Catalog:AAI9114432
OCLC Identifier:(UMI)AAI9114432

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