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Influence of density of states on optical properties of GaSe thin film
Author(s) -
Thamilselvan M.,
Premnazeer K.,
Mangalaraj D.,
Narayandass Sa. K.,
Yi Junsin
Publication year - 2004
Publication title -
crystal research and technology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.377
H-Index - 64
eISSN - 1521-4079
pISSN - 0232-1300
DOI - 10.1002/crat.200310161
Subject(s) - amorphous solid , thin film , crystallite , density of states , materials science , auger electron spectroscopy , analytical chemistry (journal) , valence (chemistry) , substrate (aquarium) , chemistry , condensed matter physics , crystallography , nanotechnology , physics , oceanography , organic chemistry , chromatography , geology , nuclear physics
A systematic investigation on the effect of substrate temperature on the structure, optical absorption and density of states of vacuum evaporated gallium monoselenide (GaSe) thin films is reported. The X‐ray diffraction analysis shows an occurrence of amorphous to polycrystalline transformation in the films deposited at higher‐temperature substrates (573K). The compositional analysis is made with Auger Electron Spectroscopy (AES). The thickness of the film (175nm) is measured by a multiple beam interferometery. Optical characteristics of the GaSe sample have been analyzed using spectrophotometer in the photon energy range of 1.0 ‐ 4 eV. The absorption mechanism has been recognized and the allowed indirect as well as forbidden direct transitions have been found. As‐deposited films show two indirect and allowed transitions due to spin‐orbit splitting of the valence band, as reported here for the first time. Low field conduction have enabled us to determine the density of states in amorphous and poly‐GaSe films. The amorphous and polycrystalline GaSe thin films have localized states density values of N (E F ) = 1.686 × 10 17 cm ‐3 eV ‐1 and 1.257 × 10 15 cm ‐3 eV ‐1 respectively. The experimental results are interpreted in terms of variations in the density of localized states due to progressive decrease of the unsaturated bonds during deposition. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)