Polar heterostructure for multi-function devices: theoretical studies

It is well known that polar oxides such as BaTiO/sub 3/ and LiNbO/sub 3/ have extremely large piezoelectric and pyroelectric effects which make them highly suitable for sensor application. Semiconductors on the other hand have poor piezoelectric and pyroelectric effects but have their abilities to show large change in conductivity with small bias. In this paper we examine the potential of devices based on heterostructures made from highly polar materials and semiconductors. Such functional devices have superior sensor properties as well as transistor properties. The basis device examined is based on the use of a thin oxide with high piezoelectric coefficients or pyroelectric coefficients under the gate region. Channel charge and current are directly controlled by gate voltage (normal FET), temperature (thermal sensor), or stress (stress sensor). We examine the performance of three classes of heterostructures that form the basis of important semiconductor technologies: (i) Si/SiO/sub 2//BaTiO/sub 3/ heterostructure junctions that would be an important breakthrough for silicon sensor technology; (ii) GaN/AlN/BaTiO/sub 3/ heterostructure junctions that would be important especially in high temperature sensor application; and (iii) GaAs/AlGaAs/BaTiO/sub 3/ heterostructure field effect transistors.