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Generic origin of subgap states in transparent amorphous semiconductor oxides illustrated for the cases of In-Zn-O and In-Sn-O

: Körner, W.; Urban, D.F.; Elsässer, C.

Preprint urn:nbn:de:0011-n-3523304 (344 KByte PDF)
MD5 Fingerprint: 64f3596f2040eecb9fb8871d27e65208
Created on: 19.5.2016

Physica status solidi. A 212 (2015), No.7, pp.1476-1481
ISSN: 0031-8965
ISSN: 1862-6300
ISSN: 1521-396X
ISSN: 1862-6319
European Commission EC
FP7-NMP; 246334; Orama
Journal Article, Electronic Publication
Fraunhofer IWM ()
amorphous materials; band tails; deep levels; gap states; transparent conductive oxides

We present a microscopic interpretation for the appearance and behaviour of subgap states in stoichiometric and oxygen-deficient, amorphous In-Zn-O (a-IZO) and In-Sn-O (a-ITO) derived from a density functional theory analysis using a self-interaction-correction scheme. Our findings concerning the defect structures and the resulting deep levels are qualitatively similar to earlier results on a-IGZO and a-ZTO and in agreement with recent experimental results. Based on our extensive set of DFT results for In-, Sn-, Zn- based oxides we develop a general concept of the subgap states which is applicable to these systems. Electronic defect levels in the lower half of the band gap are created by undercoordinated oxygen atoms while local oxygen deficiencies cause defect levels in the upper part of the band gap.