Interface characterization of all-perovskite oxide field effect heterostructures

Abstract

All-oxide devices consisting of Niobium-doped Strontium Titanate (Nb:STO)/Strontium Titanate (STO)/Lanthanum Strontium Cuprous Oxide (LSCO) heterostructures were fabricated and characterized electrically for their interface properties through capacitance-voltage (C-V) and current-voltage (I-V) techniques, in the context of electric field effect studies. The C-V studies establish the occurrence of charge modulation in the LSCO channel. Absence of hysteresis in the C-V characteristic when the voltage is retraced suggests the absence of mobile ions in the gate oxide and slow interface traps. This is further corroborated by the absence of drift in the C-V characteristic and shift in the flat band voltage (V _FB) when the device is subjected to temperature-bias aging. The interface state density obtained from V _FB is ~10¹²/cm². The uncompensated hole concentration in the LSCO channel calculated from the measured room temperature C-V data is ~10²⁰/cm³ and is in good agreement with the expected hole concentration in LSCO. Current-time and current-voltage plots are invariant with respect to the polarity of the applied voltage up to ~5 V. This, in a structure with asymmetric interfaces, indicates that the electrical contacts to STO are non-blocking and the conduction through STO is bulk-limited in this voltage regime. Thickness dependent current and capacitance studies also corroborate the bulk-limited nature of conduction through the device in this voltage regime. However, I-V characteristic shows a rectifying nature beyond ~8 V indicating that the mechanism in this voltage regime could be interface limited.