Majority-carrier mobilities in undoped and n -type doped ZnO epitaxial layers
Abstract
Transparent and conductive ZnO:Ga thin films are prepared by laser molecular-beam epitaxy. Their electron properties were investigated by the temperature-dependent Hall-effect technique. The 300-K carrier concentration and mobility were about ns ∼ 1016 cm–3 and 440 cm2/V s, respectively. In the experimental ‘mobility vs concentration’ curve, unusual phenomenon was observed, i.e., mobilities at ns ∼ 5 × 1018 cm–3 are significantly smaller than those at higher densities above ∼1020 cm–3. Several types of scattering centers including ionized donors and oxygen traps are considered to account for the observed dependence of the Hall mobility on carrier concentration. The scattering mechanism is explained in terms of inter-grain potential barriers and charged impurities. A comparison between theoretical results and experimental data is made. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
