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Title: Optical and structural study of GaN nanowires grown by catalyst-free molecular beam epitaxy. II. Sub-band-gap luminescence and electron irradiation effects

GaN nanowires with diameters of 50-250 nm, grown by catalyst-free molecular beam epitaxy, were characterized by photoluminescence (PL) and cathodoluminescence (CL) spectroscopy at temperatures from 3 to 297 K. Both as-grown samples and dispersions of the nanowires onto other substrates were examined. The properties of the near-band-edge PL and CL spectra were discussed in Part I of this study by [Robins et al. [L. H. Robins, K. A. Bertness, J. M. Barker, N. A. Sanford, and J. B. Schlager, J. Appl. Phys. 101,113505 (2007)]. Spectral features below the band gap, and the effect of extended electron irradiation on the CL, are discussed in Part II. The observed sub-band-gap PL and CL peaks are identified as phonon replicas of the free-exciton transitions, or excitons bound to structural defects or surface states. The defect-related peaks in the nanowires are correlated with luminescence lines previously reported in GaN films, denoted the Y lines [M. A. Reshchikov and H. Morkoc, J. Appl. Phys. 97, 061301 (2005)]. The CL was partially quenched by electron beam irradiation for an extended time; the quenching was stronger for the free and shallow-donor-bound exciton peaks than for the defect-related peaks. The quenching appeared to saturate at high irradiation dosemore » (with final intensity {approx_equal}30% of initial intensity) and was reversible on thermal cycling to room temperature. The electron irradiation-induced quenching of the CL is ascribed to charge injection and trapping phenomena.« less
Authors:
; ; ; ;  [1] ;  [2]
  1. National Institute of Standards and Technology, Gaithersburg, Maryland 20899 (United States)
  2. (United States)
Publication Date:
OSTI Identifier:
20979411
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 101; Journal Issue: 11; Other Information: DOI: 10.1063/1.2736266; (c) 2007 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; ABSORPTION SPECTRA; CATHODOLUMINESCENCE; CRYSTAL DEFECTS; CRYSTAL GROWTH; ELECTRON BEAMS; ENERGY GAP; EXCITONS; GALLIUM NITRIDES; IRRADIATION; MOLECULAR BEAM EPITAXY; PHONONS; PHOTOLUMINESCENCE; QUANTUM WIRES; QUENCHING; RADIATION DOSES; SEMICONDUCTOR MATERIALS; TEMPERATURE RANGE 0273-0400 K; THERMAL CYCLING; THIN FILMS