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Highly conductive and optically transparent GZO films grown under metal‐rich conditions by plasma assisted MBE
Author(s) -
Liu H. Y.,
Avrutin V.,
Izyumskaya N.,
Reshchikov M. A.,
Özgür Ü.,
Morkoç H.
Publication year - 2010
Publication title -
physica status solidi (rrl) – rapid research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.786
H-Index - 68
eISSN - 1862-6270
pISSN - 1862-6254
DOI - 10.1002/pssr.200903410
Subject(s) - molecular beam epitaxy , materials science , absorption edge , oxygen , metal , analytical chemistry (journal) , doping , blueshift , optoelectronics , absorption (acoustics) , transparent conducting film , thin film , epitaxy , photoluminescence , band gap , chemistry , nanotechnology , composite material , chromatography , metallurgy , organic chemistry , layer (electronics)
We demonstrate a critical effect of a metal‐to‐oxygen ratio on the electrical, optical, and structural properties of ZnO films heavily doped with Ga (carrier concentration in the range of 10 20 –10 21 cm –3 ) grown by plasma‐assisted molecular beam epitaxy. The as‐grown layers prepared under the metal‐rich conditions exhibited resistivities below 3 × 10 –4 Ω cm and an optical transparency exceeding 90% in the visible spectral range as well as a large blue shift of the transmission/absorption edge attributed to the Burstein–Moss shift of the Fermi level deep into the conduction band, indicating high donor concentration. In contrast, the films grown under the oxygen‐rich conditions required thermal activation and showed inferior properties. Furthermore, electrical measurements point to the nonuniform depth distribution of free carriers. An oxygen‐pressure‐dependent surface disordering is suggested to be responsible for the drastic effect of the metal‐to‐oxygen ratio on the film properties. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)