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Title: Band gaps in InN/GaN superlattices: Nonpolar and polar growth directions

The electronic structures of nonpolar short-period InN/GaN superlattices (SLs) grown in the wurtzite a- and m-directions have been calculated and compared to previous calculations for polar superlattices (grown in the c-direction). The variation of the band gaps with the composition (m, n) of the mInN/nGaN unit cells of the superlattices was examined. The band structures were obtained by self-consistent calculations based on the local density approximation to the density functional theory using the Linear-Muffin-Tin-Orbital method with a semi-empirical correction for the band gaps. The calculated band gaps and their pressure coefficients for nonpolar superlattices are similar to those calculated for bulk InGaN alloys with an equivalent In/Ga concentration ratio. This is very different from what has been found in polar superlattices where the band gaps are much smaller and vanish when the number m of InN layers in the unit cell exceeds three. A strong internal electric field is responsible for this behavior of polar structures. Experimental photoluminescence data for polar SLs agree very well with gaps calculated for the nonpolar structures. It is suggested that this is caused by screening of the electric field in the polar structures by carriers originating from unintentional defects.
Authors:
; ;  [1] ; ;  [2]
  1. Institute of High Pressure Physics, UNIPRESS, 01-142 Warsaw (Poland)
  2. Department of Physics and Astronomy, Aarhus University, DK-8000 Aarhus C (Denmark)
Publication Date:
OSTI Identifier:
22266170
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 114; Journal Issue: 22; Other Information: (c) 2013 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; 71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; ALLOYS; APPROXIMATIONS; CARRIERS; CONCENTRATION RATIO; CORRECTIONS; DENSITY FUNCTIONAL METHOD; ELECTRIC FIELDS; ELECTRONIC STRUCTURE; GALLIUM NITRIDES; INDIUM NITRIDES; MUFFIN-TIN POTENTIAL; PHOTOLUMINESCENCE; PRESSURE COEFFICIENT; SUPERLATTICES