Enhancement-mode thin-film field-effect transistor using phosphorus-doped (Zn,Mg)O channel

We report on enhancement-mode ZnO-based field-effect transistors that utilize an acceptor-doped channel. In particular, the active channel is polycrystalline ZnO doped with Mg, to increase the band gap, and P, to decrease the electron carrier concentration. Devices are realized that display an on/off ratio of 10(3) and a channel mobility on the order of 5 cm(2)/V s. HfO2 serves as the gate dielectric. Capacitance-voltage properties measured across the gate indicate that the ZnO channel is n type. The use of acceptor doping improves the control of the initial channel conductance while having a minimal impact on channel mobility relative to undoped ZnO polycrystalline channels. (C) 2004 American Institute of Physics.