“ZnO Doping By Ion Implantation”

M.HERNÁNDEZ FENOLLOSA; E.RITA; L.C.DAMONTE

San Diego, USA

Simposio; SPIE 2005, Optics & Photonics 2005; 2005

With unique optical and electronic properties, the II-VI wide bandgap (Eg=3.36eV) semiconductor ZnO is arising as a potential material for demanding technological applications, such as, blue and ultraviolet light emitters and detectors. However, its widespread utilisation is limited by the low density of carriers (particularly holes) attained by doping, mainly due to the dopants association with compensating defects. Ion implantation is a precise and in-use method to introduce dopants in semiconductors that has not been widely exploited on ZnO. In this work, we present preliminary studies on ZnO single crystals implanted with In (donor), As (acceptor) and 111Ag (acceptor). Each dopants electronic structure was investigated by means of positron annihilation lifetime (PALS) and photoluminescence (PL) measurements. PALS was carried out at room temperature (RT) in a conventional fast-fast coincidence system with two scintillator detectors. PL was performed on the surface using the 325 nm emission line of a He-Cd laser. The luminescence signals were acquired at 17K and RT using a grating monochromator coupled to a CCD as detector. For some of the crystals, the lifetime spectra revealed the presence of effective positron traps. Moreover, for all samples the luminescence spectra consist of a near-band-edge (NBE) and a deep-level (DL) emission. The evolution of the NBE and DL peak intensity ratio and the NBE peak energy shift were evaluated in function of the dopants . The observed trends will be discussed in terms of the origin, nature and charge state of the induced defects involved.