Abstract
In this review we discuss the advances in use of GaN and ZnO-based solid-state sensors for gas sensing applications. AlGaN/GaN high electron mobility transistors (HEMTs) show a strong dependence of source/drain current on the piezoelectric polarization -induced two dimensional electron gas (2DEG). Furthermore, spontaneous and piezoelectric polarization induced surface and interface charges can be used to develop very sensitive but robust sensors for the detection of gases. Pt-gated GaN Schottky diodes and Sc(2)O(3)/AlGaN/GaN metal-oxide semiconductor diodes also show large change in forward currents upon exposure to H(2) containing ambients. Of particular interest are methods for detecting ethylene (C(2)H(4)), which offers problems because of its strong double bonds and hence the difficulty in dissociating it at modest temperatures. ZnO nanorods offer large surface area, are bio-safe and offer excellent gas sensing characteristics.