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 $\mathrm{P,}$ 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 $\text{5\hspace{0.5em}}{\mathrm{cm}}^2/\mathrm{V} \mathrm{s}.$ ${\mathrm{HfO}}_2$ 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.