High resistive layers toward ZnO-based enzyme modified field effect transistor

One of the key issues for the realization of ZnO-based enzyme modified field effect transistors (FET) is growth of a high resistive layer underneath the active layer of the device structure. For that purpose, nitrogen-doped ZnO (ZnO:N) and ZnMgO layers were grown on a-plane sapphire substrates by molecular beam epitaxy (MBE). Although photoluminescence (PL) spectra indicated that nitrogen atom was incorporated as acceptor, ZnO:N layers showed still n-type conductivity probably due to generation of donor-like defects during nitrogen doping. On the other hand, ZnMgO layers showed high resistive and flat surface, which will be utilized underlying layers for successive growth of ZnO-based biosensors.