Polar heterostructure for multifunction devices: theoretical studies

We examine the potential of devices based on heterostructures made from highly polar materials and semiconductors. Our calculations show that such functional devices have superior sensor properties and 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 controlled by gate voltage, temperature, or stress. We examine the performance of three classes of heterostructures that form the basis of important semiconductor technologies: 1) Si-SiO/sub 2/-BaTiO/sub 3/ heterostructure junctions that would be an important breakthrough for silicon sensor technology; 2) GaN-AlN-BaTiO/sub 3/ heterostructure junctions that would be important especially in high temperature sensor application; and 3) GaAs-AlGaAs-BaTiO/sub 3/ heterostructure field effect transistors. The calculations show that with a very thin polar material layer we can have a highly sensitive sensor and transistor. For optimum performance, the polar material (piezoelectric or pyroelectric) layer thickness should be /spl sim/30 /spl Aring/.