Wide Bandgap Semiconductor Nanorod and Thin Film Gas Sensors

In this review we discuss the advances in use of GaN and ZnO-based solid-statesensors for gas sensing applications. AlGaN/GaN high electron mobility transistors(HEMTs) show a strong dependence of source/drain current on the piezoelectricpolarization -induced two dimensional electron gas (2DEG). Furthermore, spontaneous andpiezoelectric polarization induced surface and interface charges can be used to develop verysensitive but robust sensors for the detection of gases. Pt-gated GaN Schottky diodes and Sc2O3/AlGaN/GaN metal-oxide semiconductor diodes also show large change in forwardcurrents upon exposure to H2 containing ambients. Of particular interest are methods fordetecting ethylene (C2H4), which offers problems because of its strong double bonds andhence the difficulty in dissociating it at modest temperatures. ZnO nanorods offer largesurface area, are bio-safe and offer excellent gas sensing characteristics.