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We have grown dilute InPN layers by liquid phase epitaxy and characterized them using high resolution x-ray diffraction, optical absorption, low temperature photoluminescence, and Hall measurement techniques. Our results indicate that a maximum amount of 0.2% nitrogen has been incorporated in the material with a band gap lowering consistent with expectations. The crystalline quality of the material is found to improve upon nitrogen incorporation. Large increase in luminescence from the material is observed after a high temperature annealing. [ABSTRACT FROM AUTHOR]

The evolution of InAs quantum dots grown on InP substrates by metal-organic vapor phase epitaxy is studied as a function of InAs coverage. Under specific growth conditions, the onset of the two- to three-dimensional transition proceeds via two distinct pathways: through (i) an abrupt appearance of quantum dots as expected in the usual Stranski-Krastanov growth picture and (ii) a continuous evolution of small surface features into well-developed quantum dots. The average size of the features in both these families increases with coverage, leading to a bimodal distribution in dot sizes at an intermediate stage of growth evolution. On further deposition of material, the two families merge into a single broad unimodal distribution of sizes. Complementary information obtained from independent measurements of photoluminescence spectra and surface morphology is correlated and is found to be independently consistent with the picture of growth proposed. [ABSTRACT FROM AUTHOR]

InGaAs strained quantum well (SQW) samples with lattice matched InGaAsP quaternary barriers are grown on GaAs substrates by metalorganic vapor phase epitaxy. These SQW samples are characterized using photoluminescence, photomodulated reflectance, surface photovoltage spectroscopy and high-resolution x-ray diffraction techniques. The results based on numerical calculations are used to identify the various transitions seen in the spectra. The effect of growth temperature on the indium content of the InGaAs SQW with lattice matched InGaAsP quaternary barriers is studied. Contrary to the reported higher value of indium incorporation in InGaAs SQW with GaAs (In-free) barriers when the growth is performed at low temperatures, we find that the indium content of the InGaAs SQW with InGaAsP (In-based) quaternary barriers decreases if the SQW is grown at lower growth temperatures. A possible explanation for this behavior is provided. © 2002 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Deals with a study which examined the photoreflectance and photoluminescence spectroscopy of low-temperature gallium arsenide grown by molecular-beam epitaxy. Information on modulation-doped photodectector structures; Methodology of the study; Results and discussion.

Photoluminescence from highly disordered GaAs quantum wells is studied in magnetic fields up to 50 T. The monotonic decrease of the photoluminescence linewidth with increasing quantum well thickness indicates that interface roughness is the primary source of line broadening. The magnetic field-dependent exciton linewidth shows an unexpected behavior. We observe not only just a monotonic increase in linewidth but also a field-dependent decreasing linewidth in thicker quantum wells. These observations are understood by postulating the existence of two correlation lengths for the interface fluctuations, one much smaller than the exciton size and the other one of the order of the exciton size. [ABSTRACT FROM AUTHOR]

This letter establishes a correlation between the internal stress in InN epilayers and their optical properties such as the measured absorption band edge and photoluminescence emission wavelength. By a careful evaluation of the lattice constants of InN epilayers grown on c-plane sapphire substrates under various conditions by metalorganic vapor phase epitaxy, the authors find that the films are under primarily hydrostatic strain. The corresponding stress results in a shift in the band edge to higher energy. The effect is significant and may be responsible for some of the variations in InN bandgap reported in the literature. [ABSTRACT FROM AUTHOR]

The authors report the observation of strong polarization anisotropy in the photoluminescence (PL) and the absorption spectra of [112¯0] oriented A-plane wurtzite InN films grown on R-plane [11¯02] sapphire substrates using molecular beam epitaxy. For A-plane films the c axis lies in the film plane. The PL signal collected along [112¯0] with electric vector E ⊥ c is more than three times larger than for E ∥ c. Both PL signals peak around 0.67 eV at 10 K. The absorption edge for E ⊥ c is shifted to higher energy by 20 meV relative to E ⊥ c. Optical polarization anisotropy in wurtzite nitrides originates from their valence band structure which can be significantly modified by strain in the film. The authors explain the observed polarization anisotropy by comparison with electronic band structure calculations that take into account anisotropic in-plane strain in the films. The results suggest that wurtzite InN has a narrow band gap close to 0.7 eV at 10 K. [ABSTRACT FROM AUTHOR]

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]

Cadmium incorporation in nominally undoped n-InP using open-tube diffusion has been investigated by photoluminescence (PL) measurements. A Sn-InP solution has been used to provide P vapor overpressure during the diffusion. This results in a 2–3 times larger incorporation of Cd acceptors in InP as compared to a low P vapor overpressure condition. In addition, the overall degradation in the PL intensity is considerably reduced by this technique. The degradation in InP during diffusion is further investigated by PL measurements on heat-treated InP under the diffusion conditions. [ABSTRACT FROM AUTHOR]