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Single‐crystal gallium nitride (GaN) thin films were grown using a graphene mask via multiple epitaxial lateral overgrowth (multiple‐ELOG). During the growth process, the graphene mask self‐decomposed to enable the emergence of a GaN film with a thickness of several hundred nanometres. This is in contrast to selective area growth of GaN using an SiO2 mask leading to the well known hexagonal‐pyramid shape under the same growth conditions. The multiple‐ELOG GaN had a single‐crystalline wurtzite structure corresponding to the crystallinity of the GaN template, which was confirmed with electron backscatter diffraction measurements. An X‐ray diffraction rocking curve of the asymmetric 102 reflection showed that the FWHM for the multiple‐ELOG GaN decreased to 405 from 540′′ for the underlying GaN template. From these results, the self‐decomposition of the graphene mask during ELOG was experimentally proven to be affected by the GaN decomposition rather than the high‐temperature/H2 growth conditions. [ABSTRACT FROM AUTHOR]

The reduction of unintentional impurities in m‐plane ( 10 1 ¯ 0 ) GaN homoepitaxial layers is demonstrated by using nitrogen (N2), as opposed to hydrogen (H2), as carrier gas in metalorganic vapor phase epitaxy (MOVPE). Secondary ion mass spectrometry (SIMS) analysis shows that the impurity levels of residual oxygen (O), carbon (C), and silicon (Si) are decreased by nearly one order of magnitude in N2‐grown samples. Although the full width at half maximum (FWHM) values for the on‐axis m‐plane X‐ray rocking curves of all specimens are quite similar (around 50 arcsec), plan‐view scanning transmission electron microscopy (STEM) measurements reveal a clear reduction of dislocation densities in N2‐grown films. Their origin is likely related to an initial surface roughening with H2 carrier gas, which also causes surface faceting resulting in the formation of large four‐sided pyramidal hillocks, while using N2 results in smoother surfaces. Hence, MOVPE growth with N2 carrier gas is an effective method to lower the impurity incorporation in m‐plane GaN materials in addition to reducing the formation of defects and improving the surface morphology, which can enable the development of high‐performance GaN‐based devices on non‐polar surfaces. [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]

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]

The selective area growth (SAG) of GaN was implemented on patterned GaN/sapphire templates by hydride vapor phase epitaxy (HVPE) to fabricate regular arrays of Ga-polar GaN microrods. The control of growth parameters such as H 2 /N 2 carrier gas ratio, growth temperature, and absolute NH 3 /HCl gas flow resulted in changes in the growth morphology. In particular, for an optimized mixed-carrier gas ratio of H 2 to N 2 , we achieved vertically well-aligned microrods. The topmost regions of the GaN microrods were terminated with pyramidal facets, indicating typical Ga polarity. The optical properties of the grown microrods were characterized by cathodoluminescence (CL) at a low temperature. This revealed that the GaN microrods had high crystal quality since they exhibited suppressed yellow luminescence as well as strong band edge emission. [ABSTRACT FROM AUTHOR]

To integrate multiple functional devices on a chip, advances in epitaxial growth on heterosubstances are required. We developed a method of combined epitaxial growth using molecular beam epitaxy (MBE) and metal–organic chemical vapor deposition (MOCVD) as one approach to achieve an epitaxial layer on an amorphous substrate. This two-stage combined growth can be used to grow binary gallium nitride (GaN) on any thermally durable substance. The first MBE growth step provided effective nucleation with uniform morphology. Meanwhile, the second MOCVD growth step resulted in improved crystalline quality. Detailed analysis of grain-to-grain and layer-to-layer interfaces was performed with high-resolution transmission electron microscopy (TEM) characterization. This study gives a deep understanding of the growth behavior, thereby supporting the generation of perfect single crystalline GaN, enabling the realization of optoelectronic GaN-based devices on an amorphous layer. [ABSTRACT FROM AUTHOR]