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Title: Smooth cubic commensurate oxides on gallium nitride

Smooth, commensurate alloys of 〈111〉-oriented Mg{sub 0.52}Ca{sub 0.48}O (MCO) thin films are demonstrated on Ga-polar, c+ [0001]-oriented GaN by surfactant-assisted molecular beam epitaxy and pulsed laser deposition. These are unique examples of coherent cubic oxide|nitride interfaces with structural and morphological perfection. Metal-insulator-semiconductor capacitor structures were fabricated on n-type GaN. A comparison of leakage current density for conventional and surfactant-assisted growth reveals a nearly 100× reduction in leakage current density for the surfactant-assisted samples. HAADF-STEM images of the MCO|GaN interface show commensurate alignment of atomic planes with minimal defects due to lattice mismatch. STEM and DFT calculations show that GaN c/2 steps create incoherent boundaries in MCO over layers which manifest as two in-plane rotations and determine consequently the density of structural defects in otherwise coherent MCO. This new understanding of interfacial steps between HCP and FCC crystals identifies the steps needed to create globally defect-free heterostructures.
Authors:
; ; ; ; ; ; ; ; ;  [1] ; ;  [2]
  1. Department of Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina 27695 (United States)
  2. Center for Nanophase Materials Science, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States)
Publication Date:
OSTI Identifier:
22278078
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 115; Journal Issue: 6; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; CALCIUM OXIDES; COMPARATIVE EVALUATIONS; CRYSTAL DEFECTS; CRYSTALS; DENSITY; ELECTRON MICROSCOPY; ENERGY BEAM DEPOSITION; FCC LATTICES; GALLIUM NITRIDES; HCP LATTICES; HETEROJUNCTIONS; INTERFACES; LASER RADIATION; LAYERS; LEAKAGE CURRENT; MAGNESIUM COMPOUNDS; MOLECULAR BEAM EPITAXY; PULSED IRRADIATION; SEMICONDUCTOR MATERIALS; THIN FILMS