Highly sensitive detection of NO2 gas using BGaN/GaN superlattice-based double Schottky junction sensors

Abstract

We report a double Schottky junction gas sensor based on a BGaN/GaN superlattice and Pt contacts. NO2 is detected at concentrations from 4.5 to 450 ppm with current responsivity of 6.7 mA/(cm2 × ppm) at 250 °C with a response time of 5 s. The sensor is also selective against NH3 at least for concentrations less than 15 ppm. The BGaN layer at the surface increases surface trap density and trap depth, which improves responsivity and high temperature stability while the GaN layer improves the magnitude of the diode current. The BGaN layer's columnar growth structure also causes a Pt morphology that improves O2− diffusion.