310 research outputs found

    V-shaped inversion domains in InN grown on c-plane sapphire

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    Inversion domains with a V-shape were found to nucleate inside a Mg-doped InN heteroepitaxial layer. They resemble Al-polarity domains, observed recently, in N-polarity AlN films. However, the angle between the side-walls of the V-shaped domain and the c-axis differs in these two cases. In InN, this angle is almost two times bigger than that reported for AlN. The origin of V-shaped inversion domains in InN film is not yet clear

    Inversion domains in AlN grown on (0001) sapphire

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    Al-polarity inversion domains formed during AlN layer growth on (0001) sapphire were identified using transmission electron microscopy (TEM). They resemble columnar inversion domains reported for GaN films grown on (0001) sapphire. However, for AlN, these columns have a V-like shape with boundaries that deviate by 2 {+-} 0.5{sup o} from the c-axis. TEM identification of these defects agrees with the post-growth surface morphology as well as with the microstructure revealed by etching in hot aqueous KOH

    Correlations between spatially resolved Raman shifts and dislocation density in GaN films

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    Spatially resolved Raman spectra were measured on thick GaN samples with known dislocation density grown by hydride vapor phase epitaxy. The frequencies of the E-2 (high) and E-1 (transverse optical) phonons shift to lower wave number over a distance of 30 mum from the sapphire substrate/GaN interface. The shifts are linearly correlated with the dislocation density suggesting that the strain due to the lattice mismatch at the interface determines both quantities

    Influence of Dopants on Defect Formation in GaN

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    Influence of p-dopants (Mg and Be) on the structure of GaN has been studied using Transmission Electron Microscopy (TEM). Bulk GaN:Mg and GaN:Be crystals grown by a high pressure and high temperature process and GaN:Mg grown by metal-organic chemical-vapor deposition (MOCVD) have been studied. Structural dependence on growth polarity was observed in the bulk crystals. Spontaneous ordering in bulk GaN:Mg on c-plane (formation of Mg-rich planar defects with characteristics of inversion domains) was observed for growth in the N to Ga polar direction (N polarity). On the opposite site of the crystal (growth in the Ga to N polar direction) Mg-rich pyramidal defects empty inside (pinholes) were observed. Both these defects were also observed in MOCVD grown crystals. Pyramidal defects were also observed in the bulk GaN:Be crystals

    High resistivity and ultrafast carrier lifetime in argon implanted GaAs

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    We have investigated the optoelectronic and structural properties of GaAs that has been implanted with Ar ions and subsequently annealed. The material exhibits all the basic optical and electronic characteristics typically observed in nonstoichiometric, As implanted or low‐temperature‐grown GaAs. Annealing of Ar implanted GaAs at 600 °C produces a highly resistive material with a subpicosecond trapping lifetime for photoexcited carriers. Transmission electron microscopy shows that, instead of As precipitates, characteristic for the nonstoichiometeric GaAs, voids ranging in size from 3 to 5 nm are observed in Ar implanted and annealed GaAs. © 1996 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/69637/2/APPLAB-69-17-2569-1.pd

    Unusual luminescence lines in GaN

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    none11A series of sharp intense peaks was observed in the low-temperature photoluminescence spectrum of unintentionally doped GaN in the photon energy range between 3.0 and 3.46 eV. We attributed the majority of these peaks to excitons bound to unidentified structural and surface defects. Most of the structural- and surface-related peaks ~at 3.21, 3.32, 3.34, 3.35, 3.38, and 3.42 eV! were observed in Ga polar films. In N polar GaN, we often observed the 3.45 eV peak attributed to excitons bound to the inversion domain interfaces.SCOPUS 2-s2.0-0242496327 DOI: 10.1063/1.1609632M.A. RESHCHIKOV; D. HUANG; F. YUN; P. VISCONTI; L. HE; H. MORKOC; J. JASINSKI; Z. LILIENTAL-WEBER; R.J.MOLNAR; S. S. PARK; K.Y.LEEM. A., Reshchikov; D., Huang; F., Yun; Visconti, Paolo; L., He; H., Morkoc; J., Jasinski; Z., LILIENTAL WEBER; R. J., Molnar; S. S., Park; K. Y., Le
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