Strontium titanate field effect heterostructures

Abstract

Many epitaxial heterostructures of transition metal oxides with perovskite structure can be found in literature, accounting for the great interest on electronic devices based on correlated materials. Within this context, the role of traditional semiconductors (Si, Ge) can be played by SrTiO<SUB>3</SUB>, which can become metallic with a carrier concentration as low as 10<SUP>18</SUP> cm<SUP>-3</SUP> and with an electron mobility as high as 10<SUP>4</SUP> cm<SUP>2</SUP>/(V(DOT)s), comparable to the one commonly found in silicon. First, we studied the dramatic effect of oxygen deficiency on transport properties of SrTiO<SUB>3-(delta</SUB> ) homoepitaxial thin films deposited by Pulsed Laser Deposition (PLD) in Ultra High Vacuum (UHV) conditions. Then, we explored the feasibility of employing e-doped strontium titanate as semiconducting layer in field effect Metal-Insulator- Semiconductor (MIS) heterostructures. We deposited MIS epitaxial heterostructures, where the wide band gap insulating layer was made of MgO (E<SUB>gap</SUB> approximately equals 8 eV). Field effect measurements performed by an a.c. technique showed an increase in conductance up to 90% at 6 Volts of gate voltage. This promising result could open new perspectives in crystalline oxides electronics.