Determination of electrical types in the P-doped ZnO thin films by the control of ambient gas flow

Phosphorus (P)-doped ZnO thin films with amphoteric doping behavior were grown on c-sapphire substrates by radio frequency magnetron sputtering with various argon/oxygen gas ratios. Control of the electrical types in the P-doped ZnO films was achieved by varying the gas ratio without post-annealing. The P-doped ZnO films grown at a argon/oxygen ratio of 3/1 showed p-type conductivity with a hole concentration and hole mobility of 1.5 x 10(17) cm(-3) and 2.5 cm(2)/V s, respectively. X-ray diffraction showed that the ZnO (0 0 0 2) peak shifted to lower angle due to the positioning of P-3 ions with a larger ionic radius in the O-2 sites. This indicates that a p-type mechanism was due to the substitutional P-O. The low-temperature photoluminescence of the p-type ZnO films showed p-type related neutral acceptor-bound exciton emission. The p-ZnO/n-Si heterojunction light emitting diode showed typical rectification behavior, which confirmed the p-type characteristics of the ZnO films in the as-deposited status, despite the deep-level related electroluminescence emission. (C) 2010 Elsevier B.V. All rights reserved.