The effect of annealing on SrTiO3 field-effect transistor devices

We have investigated the effect of interface states on the performance of a field-effect transistor composed of a SrTiO3 (100) single crystal as a channel and an amorphous CaHfO3 layer as a gate insulator. The amorphous CaHfO3 gate insulator layer, which was grown at a pressure above 1 mTorr by pulsed laser deposition (PLD), had a breakdown field of over 5 MV/cm. The transistors deposited under “hard” ablation conditions, at a laser fluence of ∼1.2 J/cm2, showed a normally on conducting behavior even at zero gate bias. An annealing treatment was found to decrease the interface conductivity by filling oxygen vacancies and the annealed devices exhibited clear enhancement-type transistor action.