We have grown Mg-doped GaN films by metalorganic chemical vapor deposition with various CP 2 Mg flow rates. After 750°C postgrowth annealing, p-type GaN films with carrier concentrations and mobilities about 2ϫ10 17 /cm 3 and 10 cm 2 /V s, respectively, have been achieved. A dominant photoluminescence ͑PL͒ line around 2.9 eV was observed at room temperature. By studying the dependence of PL on excitation density at 20 K, the emission line around 2.95 eV can be attributed to a donor-to-acceptor pair transition rather than to a conduction band-to-impurity transition involving the Mg-related deep level. We suggest that the DAP transition line is caused by a Mg related deep level at about 510 meV above the valence band. It is much deeper than the acceptor level at 250 meV commonly produced by the Mg dopants.

The optical and structural characteristics of GaN films implanted with Mg and Be ions, grown by low-pressure metalorganic chemical vapor deposition were studied. The low temperature (20 K) photoluminescence (PL) spectra of annealed Mg implanted GaN show a 356 nm near band edge emission, a 378 nm donor-acceptor (D-A) transition with phonon replicas, and a 528 nm green band deep level emission. The origin of the 528 nm green band emission and the 378 nm D-A emission might be attributed, respectively, to the Mg implantation induced clustering defect and the vacancy defect in GaN film. Observations of in-plane and out-of-plane x-ray diffraction spectra for as-grown undoped, Mg implanted and rapid thermal annealed GaN suggest that ion implantation induced anisotropic strain may be responsible for the observed PL emission characteristics.

The stress state of GaN epilayers transferred onto Si substrates through a Au–Si bonding process was studied by micro-Raman scattering and photoluminescence techniques. By increasing the Au bonding thickness from 1to40μm, the high compressive stress state in GaN layer was relieved. A 10μm Au bonding layer thickness is shown to possess the maximum compressive stress relief and also the deformation potential of the quantum well was found to be ∼85meV. A nonlinear parabolic relation between luminescent bandgap and the biaxial stress of the transferred GaN epilayer in the compressive region was observed.

ZnO nanowires were grown on 2-μm-thick GaN templates by chemical vapor deposition without employing any metal catalysts. The GaN template was deposited by metal-organic chemical vapor deposition on a c-plane sapphire substrate. The diameters of the resulting nanowires were in the range of 40–250nm depending on growth time. The ZnO nanowires were vertically well aligned with uniform length, diameter, and distribution density as revealed by electron microscopy. X-ray diffraction spectra showed that ZnO grew in single c-axis orientation with the c axis normal to the GaN basal plane, indicating a heteroepitaxial relationship of (0002)ZnO‖(0002)GaN. The lattice constant of the c axis of the ZnO nanowires with diameter of 40nm was 5.211Å, which is larger than that of bulk ZnO (5.207Å). The ZnO nanowires exhibit a residual tensile strain along the c axis, which decreases with increasing diameter.

Effects of thermal annealing on deep-level defects and minority-carrier electron diffusion length in Be-doped InGaAsN J. Appl. Phys. 97, 073702 (2005); 10.1063/1.1871334Critical Mg doping on the blue-light emission in p -type GaN thin films grown by metal-organic chemical-vapor deposition J.The characteristics of p-type Mg-doped GaN films diffused with Si are studied. N-type conductivity is achieved, and the carrier mobility of diffused GaN is 90-150 cm 2 V Ϫ1 s Ϫ1 , higher than that of p-GaN but less than that of epitaxially grown n-GaN. The Mg acceptor states could become deep compensating defects, and the compensation ratio N A /N D is 0.3, 0.45, 0.6, and 0.75 for 800, 900, 1000, and 1100°C diffused GaN, respectively. The carrier transport may be dominated by electron hopping through these deep compensating centers or through diffusion. The results of temperature-dependent carrier concentration indicate that thermal annealing may induce defects at the surface, leading to an additional activation energy E d ϳ10 meV in the 200-500 K region in diffused GaN.