Improvements in structural and optical properties of wafer-scale hexagonal boron nitride film by post-growth annealing

Remarkable improvements in both structural and optical properties of wafer-scale hexagonal boron nitride (h-BN) films grown by metal-organic chemical vapor deposition (MOCVD) enabled by high-temperature post-growth annealing is presented. The enhanced crystallinity and homogeneity of the MOCVD-grown h-BN films grown at 1050 degrees C is attributed to the solid-state atomic rearrangement during the thermal annealing at 1600 degrees C. In addition, the appearance of the photoluminescence by excitonic transitions as well as enlarged optical band gap were observed for the post-annealed h-BN films as direct consequences of the microstructural improvement. The post-growth annealing is a very promising strategy to overcome limited crystallinity of h-BN films grown by typical MOCVD systems while maintaining their advantage of multiple wafer scalability for practical applications towards two-dimensional electronics and optoelectronics.11Ysciescopu

Quasi-van der Waals epitaxy of 3D GaN on 2D h-BN using MOCVD

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Defect-Mediated In-Plane Electrical Conduction in Few-Layer sp(2)-Hybridized Boron Nitrides

In-plane electrical conduction in sp(2)-hybridized boron nitride (sp(2)-BN) is presented to explore a huge potential of sp(2)-BN as an active material for electronics and ultraviolet optoelectronics. Systematic investigation on temperature -dependent current-voltage (I-V) characteristics of a few-layer sp(2)-BN grown by metal organic vapor-phase epitaxy reveals two types of predominant conduction mechanisms that are Ohmic conduction at the low bias region and space-charge-limited conduction at the high bias region. From the temperature-dependent I-V characteristics, two shallow traps with activation energies of approximately 25 and 185 meV are observed. On the basis of the near-edge X-ray absorption fine-structure spectroscopy, boron-boron (B-B) homoelemental bonding which can be related to grain boundary and nitrogen vacancy (V-N) are proposed as the origin of the shallow traps mediating the in-plane conduction in the sp(2)-BN layer. In addition, a drastic enhancement in the electrical conductivity is observed with the increasing amount of VN that acts as a donor, implying that controlled generation of V-N can be an alternative and better approach for the n-type doping of the sp(2)-BN film rather than ineffective conventional substitutional doping methods.11Nsciescopu

Role of hydrogen carrier gas on the growth of few layer hexagonal boron nitrides by metal-organic chemical vapor deposition

Few layer hexagonal boron nitride (h-BN) films were grown on 2-inch sapphire substrates by using metal-organic chemical vapor deposition (MOCVD) with two different carrier gases, hydrogen (H2) and nitrogen (N2). Structural, optical and electrical properties of the MOCVD-grown h-BN films were systematically investigated by various spectroscopic analyses and electrical conduction measurement. Based on the experimental findings including narrower X-ray photoelectron spectra, reduced intensity of the shoulder peaks in near edge X-ray absorption fine structure spectra, and decreased electrical conduction by more than three orders of magnitude when H2 carrier gas is employed, it was concluded that H2 has an advantage over N2 as the carrier gas for MOCVD growth of h-BN which is attributed to the healing of crystalline defects by etching and regrowth processes occurring under the pulsed source-injection mode

Wafer-Scale and Selective-Area Growth of High-Quality Hexagonal Boron Nitride on Ni(111) by Metal-Organic Chemical Vapor Deposition

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Optical and facet dependent carrier recombination properties of hendeca-facet InGaN/GaN micro light emitters

110sciescopu

Defect-Mediated In-Plane Electrical Conduction in Few-Layer sp²‑Hybridized Boron Nitrides

In-plane electrical conduction in sp²-hybridized boron nitride (sp²-BN) is presented to explore a huge potential of sp²-BN as an active material for electronics and ultraviolet optoelectronics. Systematic investigation on temperature-dependent current–voltage (<i>I</i>–<i>V</i>) characteristics of a few-layer sp²-BN grown by metal–organic vapor-phase epitaxy reveals two types of predominant conduction mechanisms that are Ohmic conduction at the low bias region and space-charge-limited conduction at the high bias region. From the temperature-dependent <i>I</i>–<i>V</i> characteristics, two shallow traps with activation energies of approximately 25 and 185 meV are observed. On the basis of the near-edge X-ray absorption fine-structure spectroscopy, boron–boron (B–B) homoelemental bonding which can be related to grain boundary and nitrogen vacancy (V_N) are proposed as the origin of the shallow traps mediating the in-plane conduction in the sp²-BN layer. In addition, a drastic enhancement in the electrical conductivity is observed with the increasing amount of V_N that acts as a donor, implying that controlled generation of V_N can be an alternative and better approach for the n-type doping of the sp²-BN film rather than ineffective conventional substitutional doping methods

Growth and Interface Structural Characterization of MOCVD GaN on h-BN

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Optical and Facet-Dependent Carrier Recombination Properties of Hendecafacet InGaN/GaN Microsized Light Emitters

A hendecafacet (HF) microsized light emitter based on an InGaN/GaN multiple quantum well (MQW) is grown via selective area metal–organic chemical vapor deposition. The HF microsized light emitter is found to possess four crystallographic facets, (0001), {11̅01}, {112̅2}, and {11–20}. Distinct facet-dependent emission properties, investigated by confocal scanning photoluminescence (PL) and cathodoluminescence (CL) measurements, are found to originate from differences in indium composition and InGaN quantum well thickness of the MQW. Facet-dependent recombination properties, examined by temperature-dependent micro-PL and PL streak images, suggest that the localization energy and nonradiative recombination of carriers at MQW on each facet are varied with the polarization fields and threading dislocations. Besides, scanning time-resolved PL measurements reveal that the recombination lifetime around the edge where different facets meet is shorter than that in the facet regions, implying such nonradiative recombination can be a significant obstacle for achieving high quantum efficiency microstructured light-emitting diodes