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The effect of alloy disorder on optical density of states and average room-temperature carrier statistics in Ga1-xInxNyAs1-y quantum wells is discussed. A redshift between the peak of the room-temperature photoluminescence and the surface photovoltage spectra that systematically increases with nitrogen content y is observed. The relationship between this Stokes shift and the absorption linewidth in different samples suggests that the photoexcited carriers undergo a continuous transition—from quasithermal equilibrium with the lattice to complete trapping by quantum dot like potential fluctuations—with increase in nitrogen fraction. The “electron temperatures” inferred from photoluminescence spectra are consistent with this interpretation. [ABSTRACT FROM AUTHOR]

We report the observation of a root-like structure at the interface between GaAs nanowires and the (100) single-crystal GaAs substrate. These nanowires were grown via the vapor-liquid-solid mechanism using metalorganic vapor phase epitaxy. The root-like structure extends from the base of the nanowires into the substrate and has been investigated in detail using transmission electron microscopy and high-resolution electron microscopy. While the nanowires predominantly exhibit the zinc-blende type diamond cubic structure with the growth axis parallel to <111> and growth twins perpendicular to the growth axis, the root regions have a CdTe type orthorhombic structure that has been reported to occur in GaAs only under high-pressure conditions. [ABSTRACT FROM AUTHOR]

The growth of GaAsN layers by liquid phase epitaxy, using polycrystalline GaN as the source of nitrogen, is reported. The presence of nitrogen in the grown layer is indicated by a nitrogen-related shoulder in the Fourier transform absorption spectrum and a resultant band-gap reduction of 90 meV is measured by optical transmission and photocurrent techniques. Data from photocurrent and photocapacitance measurements show the presence of a 0.7 eV electron trap in the material which originates due to nitrogen. Compared with earlier published data on GaAsN, grown by other techniques, the trap is tentatively related to (N–N) defects at As sites. [ABSTRACT FROM AUTHOR]

A comparative study of n-n[sup +] and p-n[sup +] semiconductor heterojunctions has been done using the surface photovoltage spectroscopy (SPS) in the chopped light geometry. Heterojunctions n-Al[sub 0.4]Ga[sub 0.6]As/n[sup +] GaAs and p-Al[sub 0.37]Ga[sub 0.67]As/n[sup +] GaAs and substrate n[sup +] doped GaAs have been studied in the wavelength range 600–1000 nm. A sharp decrease in SPS at the band-gap energies of AlGaAs and GaAs with a broad peak in the subband-gap region of GaAs has been observed. The magnitude of surface photovoltage (SPV), for a constant photon flux for n-n[sup +] samples, is less by more than two orders of magnitude than that for p-n[sup +] samples in the wavelength range 645–870 nm. Changes in the dipole moments due to the redistribution of excess carriers in the space-charge regions are in opposite directions of the n-n[sup +] heterojunctions giving less SPV, while for p-n[sup +] heterojunction, the changes in the dipole moments are in the same direction giving more SPV in comparison to the n-n[sup +] samples. © 1998 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The effect of alloy fluctuations on the emission barrier of the DX center in aluminum gallium arsenide (AlGaAs) is studied by constant capacitance deep level transient spectroscopy using Si-doped and Sn-doped samples grown by different growth techniques. All the samples showed single broadened peaks which were analyzed by assuming a Gaussian distribution for the emission barrier. The full width at half maximum for the emission barrier spread was found to be the same (∼0.05+0.005 eV) for all the samples and is of the same order as the reported capture barrier spread for Si-doped AlGaAs, which strongly suggests that the binding energy spread of the DX center in AlGaAs is very small. [ABSTRACT FROM AUTHOR]

Photon emission occurs from the drain gate boundary of a metal-oxide-semiconductor field-effect transistor when drain bias exceeds the drain-to-source breakdown value. Spectral measurement of luminescence has been carried out over a wide range 0.7–3.1 eV in order to understand the origin of the emission. Three different types of detectors are used to measure the luminescence spectrum. A continuous broad spectrum is observed with a peak near 1.0 eV. The emission intensity decreases almost exponentially in the higher energy range. [ABSTRACT FROM AUTHOR]