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High-quality, melt-grown ZnO crystals are reported. The reflection and emission spectra of the melt-grown samples are compared with the same spectra from high-quality, vapor-grown ZnO crystals. We isolate the reflection and emission spectra predominantly related to the intrinsic properties associated with the wurtzite structure of the crystals. The quality of the crystals is reflected in the spectral reproduction of the intrinsic properties of the crystals. Both the ground state and the n=2 state of the free excitons associated with the A, B, and C valence bands of the crystals are spectrally observed in reflection. Assuming a hydrogenic character for the free excitons, the binding energy of these excitons associated with all three valence bands was determined. For the intrinsic emission spectra, attention was focused on the A-band free excitons and related optical parameters. Both the reflection and emission spectra for the melt-grown material compared very closely with the same spectra observed from high-quality vapor-grown ZnO samples. The details of both the reflection and emission spectra verify the high-quality of the melt-grown material. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Emission and reflection spectra from AlGaN/GaN single heterostructures grown on SiC substrates were investigated. Two-dimensional electron gas (2DEG) transitions were observed in both emission and reflection. The transitions are sharp, associated with the excited state of the 2DEG, reflect the conservation of the K-selection rule, and are excitonlike. The transitions are also associated with both the A- and B-valence bands. To verify the origin of the reflection and emission spectra, the top AlGaN layer was removed by reactive ion etching. After etching, only the excitonic reflection and emission spectra associated with GaN were observed. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Compares photoluminescence (PL) measurements on the two polar faces of ZnO. Crystal structure of ZnO; Difference between the PL measurements on the two faces.

Reports that high quality GaN crystals can be grown on sapphire by hydride vapor phase epitaxy. Strain produced by the thermal expansion mismatch between sapphire and GaN in the GaN crystals; Shifts in the photoluminescence and reflectance line positions.

Presents a study that determined the effective mass of an electron indium phosphide from Zeeman splittings of the donor 2P level using high-resolution photoluminescence spectroscopy. Definition of the Zeeman effective mass in terms of the energy difference; Characteristics of the samples used; Description of a radiative recombination of an exciton bound to a neutral donor where the final state is the donor in the ground or in the excited configuration.

Focuses on the observation of the donor-bound light-hole free exciton in AlGaAs-gallium arsenide quantum wells. Neutral donor-bound heavy-hole free-exciton transition; Basis for the calculations; Observation of monolayer fluctuations.

Presents a study which utilized the Fabry-Perot cavities to obtain experimental values for the quantity near the absorption edge in gallium arsenide at 2 krypton. Spectral analysis of photoluminescence; Oscillations from the Fabry-Perot cavity; Conditions necessary to form the cavity.

Presents a study which calculated the recombination lifetimes for donor-acceptor (D-A) pairs in gallium arsenide (GaAs). Observation of a group of photoluminescent lines in the energy in GaAs; Characteristics of the lifetimes D-A recombinations in GaAs; Activation of energies of D-A pairs.

Analyzes the quality of Al[subx]Ga[sub1-x]As crystals by the photoluminescence (PL) technique. Data on free and bound exciton transitions; Information on the densitometer trace of the exciton transitions in the sample.

Presents a study that investigated the deep-center hopping conduction in gallium nitride. Electrical and optical measurements; Explanation of the hopping conduction.

Investigates the optical reflectance in gallium arsenide/aluminum gallium arsenide quantum wellls. Description of the reflectance spectra display; Reason for the occurrence of the forbidden transitions; Features of the broadband specular reflectance spectroscopic technique which have been employed.

The excitons involved in this study are the longitudinal and the Γ[SUB5] and Γ[SUB6] free excitons, as well as the donor bound exciton (D[SUB0],X). The temperature dependence of the energy positions of the Γ[SUB5], Γ[SUB6], and (D[SUB0],X) excitons are well accounted for by the Varshni equation (Y. P. Varshni, Physica (Amsterdam) 34, 149 (1967)). In the same temperature range, the energy positions of the longitudinal excitons depart from the predictions of the Varshni equation. The separation between the longitudinal- and transverse-mode free excitons has been previously reported. One component of this separation is the polarizability, which has a temperature dependence. The longitudinal exciton therefore has a band-gap temperature dependence, predicted by the Varshni equation, as well as an additional dependence due to polarizability. This temperature dependence has been accounted for by the Varshni equation, plus an additional linear and a quadratic temperature dependent term. [ABSTRACT FROM AUTHOR]

An emission band at 2.4 eV, called the green band, is observed in most ZnO samples, no matter what growth technique is used. Sometimes this band includes fine structure, which consists mainly of doublets, repeated with a longitudinal-optical-phonon-energy spacing (72 meV). We have developed a vibronic model for the green band, based on transitions from two separate shallow donors to a deep acceptor. The donors, at energies 30 and 60 meV from the conduction-band edge, respectively, are also found from Hall-effect measurements. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Two low-temperature photoluminescence lines in GaN, in the region of energies commonly interpreted as longitudinal optical-phonon replicas of free excitons, donor-bound excitons, or acceptor-bound excitons, are reinterpreted as acceptor-bound excitons (A[sup 0]X's) collapsing to n=2 and n=3 excited states, respectively, of the acceptors involved. Application of this model to two sets of A[sup 0]X-related lines in hydride-vapor-phase-grown GaN gives acceptor energies of 85±1, and 115±1 meV, respectively. The existence of such shallow acceptor states, if confirmed, is of great technological importance. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Presents a study which developed zinc oxide crystals by vapor-phase techniques and by the hydrothermal method. Methodology; Results.

Focuses on a study which analyzed coupling in In[subx]Ga[sub1-x]As-GaAs coupled double quantum well structures. Angular momentum of holes associated with the quantum well; Description of the structure; Information on photoluminescence and photoluminescence excitation spectra.

Describes the magnetic field splitting and strain splitting of the emission lines in the 1.5040-1.5110 electronvolt range in GaAs. Information on the shallow donor-acceptor pair model; Description of the splitting patterns for shallow donor-acceptor centers in a zinc-blende lattice; Analysis of nine lines for hole g values.

Presents a study which investigated the optical absorption of intersubband transition in n-type gallium arsenide/Al[sub0.4]Ga[sub0.6]As multiple quantum wells with superlattice barriers as a function of temperature. Theoretical background; Methodology; Results.