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Presents a study that investigated the effects of several parameters in the diffusion conditions for copper into gallium arsenide on the photoluminescence band and bound excitons. Measurement of the photoluminescence of gallium arsenide; Analysis of the electrical measurements of the gallium arsenide; Examination of the acceptor nature of the bound excitons.

We report on photoluminescence (PL) spectroscopy and electron microscopy studies of an AlGaN quantum well (QW) structure grown by molecular beam epitaxy under metal-rich conditions with substrate rotation. Both techniques reveal unintentional formation within the AlGaN barriers of a quasiperiodic structure of thin Ga-rich layers, whose period is controlled by both the substrate rotation rate and the AlGaN growth rate. These compositional modulations act as 1-3 monolayer thick QWs emitting below 250 nm with an internal quantum efficiency (IQE) as high as ~30% at room temperature under weak excitation. Variational calculations of the QW exciton properties indicate that the observed high IQE can result from strong three-dimensional localization of the excitons confined in the narrow QWs. [ABSTRACT FROM AUTHOR]

Cathodoluminescence (CL) and transmission electron microscopy studies of homoepitaxially grown m-plane Mg-doped GaN layers are reported. Layers contain basal plane and prismatic stacking faults (SFs) with ∼106 cm-1 density. Broad emission peaks commonly ascribed to SFs were found to be insignificant in these samples. A set of quite strong, sharp lines were detected in the same spectral region of 3.36-3.42 eV. The observed peaks are tentatively explained as excitons bound to some impurity defects, which can also be related to SFs. Donor-acceptor pair (DAP) recombination involving Si or O and Mg was ruled out by fitting DAP energies and CL mapping. [ABSTRACT FROM AUTHOR]

Abstract: Time-resolved photoluminescence (TRPL) data for temperatures 2–150K are presented for two thick HVPE samples grown in two different laboratories. The samples both have residual O and Si shallow donor concentrations in the 1016 cm−3 range. The radiative decay time for neutral donor-bound excitons (DBEs) related to these donors is found to be about 300ps. The decay of the DBEs at longer decay times is found to be related to feeding from the free exciton–polariton states. At elevated temperatures the decay of the DBE is very similar to the free exciton decay. [Copyright &y& Elsevier]

Abstract: We present photoluminescence (PL) data for deliberately O-doped, high-resistive GaN samples where a new shallow donor-bound exciton (DBE) peak at about 3.4746eV (corrected for strain shift) at 2K appears. This DBE is strongly enhanced upon annealing in the entire range 450–900°C. The possible relation of this DBE to a metastable H donor state is discussed. [Copyright &y& Elsevier]

Abstract: The characteristic optical spectra for shallow donors and acceptors in GaN are discussed. The most accurate photoluminescence (PL) data are obtained from samples grown on freestanding GaN substrates, where strain shifts are absent and a low spectroscopic line width is obtained. Recent PL data for excitons bound to the O and Si donors are discussed in some detail, giving accurate values for the binding energies and excited bound donor states. The Mg-acceptor is the most important one for p-doping, but the related optical spectra are controversial. We show that there are two acceptors present in Mg-doped GaN, with two different acceptor bound exciton peaks, and also two corresponding lower energy donor–acceptor pair spectra. We give tentative evidence for their interpretation. [Copyright &y& Elsevier]

Optical properties of GaN layers grown by the molecular-beam epitaxy (MBE) and chloride-hydride vapor-phase epitaxy (CHVPE) have been studied, and the quality of two types of samples has been compared. The photoluminescence spectra have an excitonic nature for both types of layers. To determine precisely the nature of exciton transitions, the reflectance spectra were studied. A key point was the investigation of phonon-assisted exciton luminescence, which provides information on the density distribution of the exciton states. Temperature dependences of the exciton transition energy and the ratio of intensities of one- and two-phonon replicas were studied. The high quality of both types of layers has been confirmed, though the concentration of acceptors in MBE-grown samples is higher than in CHVPE samples. [ABSTRACT FROM AUTHOR]

The bound exciton recombination properties in freestanding GaN layers of various thicknesses grown by halide vapor phase epitaxy have been characterized by time-resolved spectroscopy. Improvement of the donor bound exciton (D0X) lifetime was observed with increasing GaN layer thickness up to ∼400 μm, while for thicker layers the recombination time of D0X shows a tendency to saturate. The thickness-dependent behavior of the D0X decay can be understood in terms of competition between two nonradiative mechanisms: one of which is connected to structural defects, and consequently more important for thinner layers, while for layers with thickness above 400 μm with low structural defect density the recombination time is limited by point defects such as impurities and vacancies. [ABSTRACT FROM AUTHOR]

Examines the influence of silicon doping on exciton localization in modulation-doped GaN/Al[sub 0.07]Ga[0.93]N multiple-quantum-well structures. Use of photoluminescence (PL) and time-resolved PL measurements; Evaluation of temperature dependence of radiative and non-radiative lifetime; Consistency of PL decay time.

It is demonstrated that the photoluminescence spectra of single self-assembled InAs/GaAs quantum dots are very sensitive to excitation energy and crystal temperature. This is qualitatively explained in terms of the effective diffusivity of photogenerated particles, which affects the capture probability of the quantum dot. As a consequence, this opens the possibility of controlling the average number of excess electrons in the quantum dot by optical means. This technique may be used as a simple tool to create and study charged exciton complexes without any specially fabricated samples. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Focuses on the temperature-dependent time-resolved photoluminescence measurements on thick gallium arsenide (GaN) layers grown by hydride vapor-phase epitaxy on aluminum oxide substrates. Radiative lifetimes for the neutral-donor-bound exciton; Dominant mechanism responsible for the nonradiative recombination of the bound excitons.

Distinctly different exciton properties in pseudomorphic and strain relaxed ZnCdSe/ZnSe structures grown on GaAs are demonstrated. For pseudomorphic or partly strained structures temperature stability of photoluminescence depends on the distance from the ZnCdSe quantum well to GaAs/ZnSe interface and less on confinement energies. Densities of two-dimensional localized states and averaged localization energies, as seen by excitons, are determined from the photoluminescence kinetics measurements. These values are compared with the ones reported for contemporary GaAs/AlGaAs structures. © 1996 American Institute of Physics. [ABSTRACT FROM AUTHOR]