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Abstract: A detailed study is presented on the influence of Mn-doping on densities of screw (c-type) and edge (a-type) threading dislocations (TDs) in Ga1− x Mn x N grown by metal organic chemical vapor deposition (MOCVD) by using high-resolution X-ray diffraction (XRD). Three regions were present in Mn source rate dependence plots of density of c-TDs, and the mean twist angle corresponding to the density of a-TDs. In each region, Mn-doping exhibits different effects on the densities of a- and c-TDs, which is attributed to different dependences of the two types of TD on stresses. The results obtained from X-ray diffraction are consistent with those of atomic force microscope (AFM) measurements. It is further suggested that similar phenomena would occur when doping other elements into GaN grown by MOCVD. [Copyright &y& Elsevier]

Electrical properties of GaN-based heterostructures adopting InAlN/AlGaN bilayer barriers are investigated by Hall-effect and current–voltage measurements. It is found that this structure possesses both merits of high two-dimensional electron gas (2DEG) density and low gate leakage current density, while maintaining high 2DEG mobility. Furthermore, temperature dependence of the 2DEG density in this structure is verified to follow a combined tendency of InAlN/GaN (increase) and AlGaN/GaN (decrease) heterostructures with increasing temperature from 90 K to 400 K, which is mainly caused by superposition of the effects from carrier thermal activation induced by extrinsic factors in InAlN layer and the reduced conduction-band discontinuity. [ABSTRACT FROM AUTHOR]

Abstract: InGaN/GaN quantum wells (QWs) with symmetrical ultra thin (about 0.5nm) low temperature GaN (LT-GaN) layers bounding each InGaN layer were grown by metal-organic vapor phase epitaxy (MOVPE). From the high resolution X-ray diffraction (HR-XRD) measurement, it showed improved well-barrier interface abruptness compared to the reference MQWs without the LT-GaN layers. In addition, the V-defect density and surface roughness were reduced, especially with the depth of V-defect as low as 0.7nm. Based on the temperature dependence photoluminescence (TDPL) experiments, the internal quantum efficiency (IQE) was increased from 21.2% to 30.1% by inserting the LT-GaN layers. The carrier lifetime obtained from room temperature time resolved photoluminescence (TRPL) measurement was 7.95ns, which was longer than 5.34ns for reference MQWs. These results indicated that these additional symmetrical thin LT-GaN layers enhanced the mobility of indium and gallium atoms as well as suppressed the indium desorption for growth high quality InGaN layers and in turn improved its structural and luminescence properties. [Copyright &y& Elsevier]

Abstract: Optically specular a-plane GaN was grown on r-sapphire substrate by metal–organic chemical vapor deposition (MOCVD). Surface morphology and crystal structure anisotropic behavior related to defects with a specific distribution were characterized by X-ray diffraction (XRD) and atomic force microscopy (AFM). Cathodoluminescence (CL) images and depth-profiling spectra show Basel stacking faults (BSFs) related emission at 3.42eV, yellow band emission at 2.25 and 3.00eV emission bands of the a-plane GaN. From the results of CL and transmission electron microscopy (TEM), the origin of the blue emission band was attributed to donor–acceptor pair (DAP) emission correlated with prismatic stacking faults (PSFs). [Copyright &y& Elsevier]

Abstract: The vertical conductivity of the p-Al0.11Ga0.89N/GaN SLs has been measured and calculated. The measured result (1.35×10−5 Scm−1) is in good agreement with the calculated result (2.26×10−5 Scm−1), indicating that the adoption of Fermi–Dirac distribution and sequential tunneling model in our calculation is very plausible. As a result, it is suggested that in p-AlGaN/GaN SLs the Fermi–Dirac distribution need to be considered in calculation related to hole distribution. [Copyright &y& Elsevier]

Abstract: The influence of various annealing temperatures on microstructure evolution of oxidized Ni(20nm)/Au(20nm) ohmic contact to p-GaN was studied by synchrotron X-ray diffraction (XRD). In association with the variation of the specific contact resistance (ρ c), it is observed that NiO and Au began to form partially epitaxial structure on p-GaN at 450°C, which played a critical role in lowering down the ρ c. At 500°C, the epitaxial structure of Au and NiO was improved further while the lowest ρ c was reached. However, at 600°C, the epitaxial structure of NiO was transformed to polycrystalline structure again with a sharp increase of ρ c. Therefore, it is suggested that the degradation of the epitaxial structure of NiO is responsible for the sharp increase of ρ c. [Copyright &y& Elsevier]

Abstract: The annealing time-dependent diffusion behavior of oxidized Au/Ni/p-GaN ohmic contact was studied with Rutherford backscattering spectroscopy/Channeling (RBS/C). It was found that, at 500°C, 1min annealing caused obvious indiffusion of Au, O and outdiffusion of Ni. And the Au even has diffused to the p-GaN/metal interface. According to the annealing time-dependent RBS spectra and referring to the correspondent specific contact resistance of the samples, it is suggested that indiffusion of Au and formation of NiO at the interface are among the critical mechanisms for the formation of low resistance ohmic contact with Au/Ni/p-GaN contact structure. [Copyright &y& Elsevier]

Abstract: We report the growth and characterization of the AlGaN on low temperature (LT) AlN interlayer (IL) and effect of AlN IL on incorporation efficiency of Al composition in the AlGaN. The AlGaN layers were grown on AlN ILs by metalorganic vapor phase epitaxy (MOVPE) and characterized by X-ray diffraction (XRD) and MeV He ion Rutherford backscattering spectrometry (RBS) and cathodoluminescence (CL), the results indicate that introduction of double AlN IL resulted in an increase in Al composition incorporation efficiency. [Copyright &y& Elsevier]