Fabrication of p-type doped ZnO thin films using pulsed laser deposition

Two new methods were investigated for the fabrication of p-type doped ZnO thin films in a conventional pulsed laser deposition apparatus, but using only pure materials as targets. One of these is a sequential method and consists in firing alternatively the laser on a pure ZnO target and either a monocrystalline InP target (for phosphorus doping) or a Bi2O3 ceramic target (for bismuth doping). The other method consists in taking advantage of the lithium diffusion into a ZnO thin film while being deposited on a c-LiNbO3 substrate at high temperature. Some structural and electronic properties of the ZnO material obtained using these methods were measured using secondary ion mass spectrometry, X-ray diffraction, laser photoluminescence and Hall apparatus respectively and compared with those obtained for pure n-type thin films. The main results of this study are as follows. The sequential deposition method was successful in incorporating InP in ZnO films but led to inhomogeneous In and P spatial distributions, while segregation of Bi2O3 within the ZnO was evidenced by both the X-ray diffraction and photoluminescence results. Electrical measurements have revealed n-type conductivity for the ZnO/InP and the ZnO/c-LiNbO3 thin films and a peculiar behaviour for the ZnO/Bi2O3 samples which could point out to successful p-type doping for films containing smaller amounts of Bi2O3. (C) 2005 Springer Science + Business Media, Inc.