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Title: Defects, strain relaxation, and compositional grading in high indium content InGaN epilayers grown by molecular beam epitaxy

We investigate the structural properties of a series of high alloy content InGaN epilayers grown by plasma-assisted molecular beam epitaxy, employing the deposition temperature as variable under invariant element fluxes. Using transmission electron microscopy methods, distinct strain relaxation modes were observed, depending on the indium content attained through temperature adjustment. At lower indium contents, strain relaxation by V-pit formation dominated, with concurrent formation of an indium-rich interfacial zone. With increasing indium content, this mechanism was gradually substituted by the introduction of a self-formed strained interfacial InGaN layer of lower indium content, as well as multiple intrinsic basal stacking faults and threading dislocations in the rest of the film. We show that this interfacial layer is not chemically abrupt and that major plastic strain relaxation through defect introduction commences upon reaching a critical indium concentration as a result of compositional pulling. Upon further increase of the indium content, this relaxation mode was again gradually succeeded by the increase in the density of misfit dislocations at the InGaN/GaN interface, leading eventually to the suppression of the strained InGaN layer and basal stacking faults.
Authors:
; ; ; ; ;  [1] ; ;  [2] ;  [3] ;  [4]
  1. Physics Department, Aristotle University of Thessaloniki, GR 541 24 Thessaloniki (Greece)
  2. Microelectronics Research Group (MRG), IESL, FORTH, P.O. Box 1385, 71110 Heraklion Crete, Greece and Physics Department, University of Crete, Heraklion Crete (Greece)
  3. Department of Electronic & Electrical Engineering, University of Sheffield, Sheffield S1 3JD (United Kingdom)
  4. Institute of High Pressure Physics, Polish Academy of Sciences, Sokolowska 29/37, 01-142 Warsaw (Poland)
Publication Date:
OSTI Identifier:
22492831
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 118; Journal Issue: 15; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; ALLOYS; DEPOSITION; DISLOCATIONS; FILMS; GALLIUM NITRIDES; INDIUM; MOLECULAR BEAM EPITAXY; RELAXATION; STACKING FAULTS; STRAINS; TRANSMISSION ELECTRON MICROSCOPY