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Photoconductivity of Ga doped polycrystalline ZnO films grown by reactive plasma deposition
Author(s) -
Kishimoto Seiichi,
Hayashi Kunihiko,
Hamaguchi Hirofumi,
Makino Hisashi,
Yamada Takahiro,
Miyake Aki,
Yamamoto Tetsuya
Publication year - 2007
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/pssb.200675142
Subject(s) - photoconductivity , materials science , thin film , doping , absorption edge , optoelectronics , crystallite , absorption (acoustics) , analytical chemistry (journal) , band gap , nanotechnology , chemistry , composite material , chromatography , metallurgy
Photoconductivity and photo‐absorption of polycrystalline Ga‐doped ZnO (GZO) thin films with film thickness of 200 nm have evaluated compared with undoped ZnO films. The GZO and undoped ZnO thin films were deposited on alkali‐free glass substrate at 200 °C by a reactive plasma deposition with DC arc discharge technique under an oxygen gas flow rate from 0 to 30 sccm. Undoped ZnO films with carrier concentration of 2.50 × 10 18 and 7.96 × 10 18 cm –3 have exciton absorption at about 3.28 eV. For these films, the photoconductivity peak is agreement with the photon‐energy of exciton absorption in the optical‐absorption. The optical band edge of undoped ZnO films estimated from the optical‐absorption shows a shift to higher energy with increasing the carrier concentration. The increase of oxygen gas flow rate led to the resistivity change of GZO films from 2.15 × 10 –4 to 4.54 × 10 –3 Ω cm, corresponding to the carrier concentration change from 1.39 × 10 21 to 1.05 × 10 20 cm –3 . The photoconductivity of GZO film is larger than that of undoped ZnO film. The peak energy of photoconductivity spectra of GZO films are seen to little shift to higher energy with increasing the carrier concentration. The GZO film exhibited the larger photoconductivity at the wavelength, ranging widely less than 380 nm. GZO film with carrier concentration more than 1 × 10 21 cm –3 indicated much larger photoconductivity. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)