Highly sensitive detection of NO_2 gas using BGaN/GaN superlattice-based double Schottky junction sensors

摘要

We report a double Schottky junction gas sensor based on a BGaN/GaN superlattice and Pt contacts. NO_2 is detected at concentrations from 4.5 to 450 ppm with current responsivity of 6.7 mA/(cm~2 × ppm) at 250 ℃ with a response time of 5 s. The sensor is also selective against NH_3 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 O_(2-) diffusion.