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In this study, GaN m-plane Schottky barrier diodes fabricated with a metalorganic vapor-phase epitaxy on a GaN substrate were investigated using emission microscope, photoluminescence, and cathodoluminescence. In addition, facet dependence of leakage current under reverse-biased condition was observed. We showed that the leakage-current distribution was caused by the facet dependence of the carrier concentration and oxygen concentration. These results can provide important suggestions for the fabrication of m-plane devices. (a) four-faceted hillocks on m-plane GaN MOVPE sample, facet dependence of (b) leakage current and (c) PL peak intensity of the m-plane GaN Schottky barrier diode. [ABSTRACT FROM AUTHOR]

In this study, by using time-of-flight (TOF) high-resolution and high-sensitivity mass spectrometry measurements, the decomposition of trimethylgallium into dimethylgallium and monomethylgallium along with its adduct formation with NHx in a commercially available horizontal metalorganic vapor-phase epitaxy (MOVPE) reactor with a resistive heater was investigated and observed in more detail than previously reported. The results confirmed the use of the TOF monitoring system in analyzing the elementary reaction process in actual MOVPE systems. [ABSTRACT FROM AUTHOR]

Injecting current with a uniform carrier concentration is important for applications with three-dimensional architectures such as vertical power devices or displays. In III-nitride nanostructures, dopants not only incorporate differently depending on the surface orientation but can also seriously affect the kinetic equilibrium shapes of the nanorods. Herein, we report selective-area growth of doped GaN nanorods grown by pulsed-mode metalorganic chemical vapor deposition. Two dopants, Si and Mg, were employed as donor and acceptor atoms, respectively, for a mono-doping approach. Furthermore, a mixed flow of Si and Mg was supplied for a co-doping approach. We compared the morphological effects and growth rates of each doped GaN nanorod array. Then, we proposed appropriate growth mechanisms for the doped GaN nanorods on the basis of our structural characterizations. These results might extend the morphological functionality of GaN nanorods by including doping and may also provide an appropriate foundation for the design of nanostructure-based electronic or photonic devices. [ABSTRACT FROM AUTHOR]

A set of GaN/GaInN single quantum wells (SQWs) were grown on c-plane GaN/sapphire templates using metal organic vapor phase epitaxy (MOVPE) and atomic layer epitaxy (ALE). The structural information on the interfaces and surfaces was obtained by fitting the experimental X-ray spectra and was compared between MOVPE and ALE mode. The X-ray crystal truncation rod (CTR) scattering measurement results showed that the samples grown by ALE had sharper interfaces than those grown by MOVPE. Both the X-ray reflectivity (XRR) curve-fitting results and atomic force microscope (AFM) results indicated that the surfaces of the ALE-grown SQWs were smoother than those of MOVPE-grown SQWs. (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

Highlights • A high-resolution time-of-flight mass spectrometry system was employed. • In-situ monitoring of vapor phase reaction was demonstrated. • Decomposition of NH 3 in the simple reactor was measured. Abstract The decomposition of ammonia (NH 3) in nitrogen (N 2) ambient was studied under non-equilibrium conditions similar to those in a metal organic vapor phase epitaxy (MOVPE) reactor during the epitaxial growth of group-III nitrides. The gas phase was sampled at different positions and analyzed using a time-of-flight mass spectrometry system with a high resolution (better than 0.002 u). Our results expand earlier findings. Even at the high temperature of 1200 °C, only 26% of NH 3 decomposed in a clean metal-free reactor, whereas a higher ratio of NH 3 decomposition was realized in the presence of stainless steel. The activation energy in the clean reactor was calculated to be 0.965 ± 0.004 eV. These results demonstrate the capability of our setup and shed new light on the elucidation of the vapor phase growth mechanism of group III-nitrides by MOVPE. [ABSTRACT FROM AUTHOR]

Highlights • PL intensities of long-wavelength MQWs increased at the same indium content. • Photoluminescence emission became narrow. • The topography of long-wavelength MQWs was improved by this method. Abstract Wafer trays with different gaps (the distance between the top of the pocket and the bottom of the wafer) were used to grow InGaN/GaN multiple quantum wells (MQWs) in a horizontal metalorganic vapor phase epitaxy (MOVPE) reactor. The numerical reactor simulation revealed that at the similar surface temperature the gas phase temperature around the wafer increases due to an increased wafer tray temperature. This increased gas phase temperature is expected to increase the effective V/III ratio by enhanced NH 3 decomposition. Photoluminescence (PL) intensities of long-wavelength MQWs increased at the same indium content by the enhanced gas phase temperature, while the emission became narrow. This is related to a smoother topography at higher gas phase temperatures. [ABSTRACT FROM AUTHOR]

Highlights • Ga-polar untwinned (1 0 −1 3) GaN was obtained by directional sputtering. • FWHM values are less than 550 aresec. • Al nucleation layer in directional sputtering affects the GaN layer much. Abstract Directional sputtering of Al and AlN on (1 0 −1 0) sapphire was used to obtain metal-polar (1 0 −1 3) templates. After overgrowth with AlN and GaN using metal-organic vapor phase epitaxy, we obtained untwinned (1 0 −1 3) GaN layers. Full width at half maximum of the X-ray rocking curve of symmetric (1 0 −1 3) GaN is less than 550 arcsec along both [3 0 −3 −2] GaN and [1 −2 1 0] GaN directions. Ga-polarity of the layers was confirmed by high-resolution scanning transmission electron microscopy. Careful optimization of time and temperature of the initial Al sputtered layer was a key parameter to achieve high quality GaN templates. [ABSTRACT FROM AUTHOR]

Hexagonal boron nitride (h-BN) was directly grown on sapphire substrate using alternating ammonia (NH 3 ) and triethylboron (TEB) supply (pulsed mode) in metalorganic vapor phase epitaxy. The best condition is when just enough NH 3 is supplied to fully convert the TEB within one cycle. Excess NH 3 caused islands on h-BN film surface while a lack of NH 3 does not form h-BN at all. The epitaxial relationship between grown h-BN layer and c -plane sapphire was confirmed to be [0001] h-BN ∥[0001] sapphire and [10-10] h-BN ∥[11-20] sapphire . It is known that, compared to AlN, BN requires higher V/III ratios for good crystallinity, which due to severe gas-phase reactions is difficult to achieve using continuous supply. Thus using pulsed mode the FWHM of the symmetric (0002) diffraction was almost halved and the growth rate was several times faster. [ABSTRACT FROM AUTHOR]

The planar epitaxial growth of semipolar (10 1 ¯ 3) GaN on a Si(001) substrate was performed on a directionally sputtered AlN buffer layer. Three types of interlayers, i.e., single AlN, double AlN, and a stack of AlN/GaN layers were grown by metalorganic chemical vapor deposition (MOCVD) to achieve high quality GaN films. The results for the stack of AlN/GaN layers provide highest crystal quality and optical properties for GaN. Comparing the top (Ga face) and bottom (N face) surfaces of grown semipolar (10 1 ¯ 3) GaN confirms the defect density reduction that is due to the application of interlayers. Moreover, reduced inversion domain density on the bottom surface is attributed with the insertion of interlayers. Improving the quality of semipolar GaN on Si(001) substrates is expected to be useful for GaN/Si(001) integrated optoelectronics. [ABSTRACT FROM AUTHOR]

Abstract: We present a study of high quality (11¯01) GaN films and the InGaN/GaN multiple quantum wells (MQWs) using epitaxial lateral overgrowth (ELO) technique by atmospheric pressure metal organic chemical vapor deposition (MOCVD). The smooth coalescence of the stripes and surface morphology was measured by scanning electron microscope (SEM) and atomic force microscopy (AFM). Due to reduction in internal electric field, semipolar InGaN/GaN MQWs have higher radiative recombination rate from time-resolved photoluminescence (TRPL) measurement. In addition, from degree of polarization (DOP) measurement, we observed higher polarization ratio attributed to the induced anisotropic compressive strain. [Copyright &y& Elsevier]

Abstract: Semi-polar (112¯2) GaN layers were selectively grown by metal organic chemical vapor phase epitaxy on patterned Si (311) substrates without SiO2 amorphous mask. The (112¯2) GaN layers could be selectively grown only on Si (111) facets when the stripe mask width was narrower than 1μm even without SiO2. Inhomogeneous spatial distribution of donor bound exciton (DBE) peak in low-temperature cathodoluminescence (CL) spectra was explained by the difference of growth mode before and after the coalescence of stripes. It was found that the emission intensity related crystal defects is drastically decreased in case of selective growth without SiO2 masks as compared to that obtained with SiO2 masks. [Copyright &y& Elsevier]

Abstract: Adopting anisotropy etching method, a (111) facet of Si is obtained on a Si substrate and selective area growth (SAG) of GaN is performed with metal-organic vapor phase epitaxy on the facet. The epitaxial lateral overgrowth of (11¯01), (112¯2) GaN is investigated on (001) and (113) Si substrate, respectively, and the incorporation properties of Si, C, and Mg elements are discussed in relation to the atomic configuration on the surface. Analyzing the optical and electrical properties of C-doped (11¯01) GaN layer, it is shown that carbon creates a shallow acceptor level. On the thus prepared (11¯01) GaN layer, a light emitting diode (LED) with a C-doped p-type layer is fabricated. [Copyright &y& Elsevier]