Enhancing hydrogen sensitivity of porous GaN by using simple and low cost photoelectrochemical etching techniques

This paper reports the studies of Pd Schottky contact on porous n-GaN for hydrogen gas sensor. A simple conventional and low cost photoelectrochemical etching method was used to produce porous GaN with high uniformity. Hydrogen sensor was subsequently fabricated by depositing Pd Schottky contacts onto the porous GaN sample. For comparative study, a standard hydrogen sensor was also prepared by depositing Pd Schottky contacts on the as-grown sample. The Pd/porous GaN sensor exhibited a significant change of current upon exposure to different flow rates of 2% H2 in N2 gas as compared to the standard Pd/GaN sensor. The response increased exponentially with hydrogen flow rate for both sensors, but Pd/porous GaN is more sensitive to hydrogen than that of the as-grown GaN. The values of ideality factor (n), barrier height (φB) and series resistance (Rs) were calculated in both sensors. Barrier heights and series resistance decreased with H2 flow rate while ideality factor increased.