Hydrogen sensing characteristics of non-polar a-plane GaN Schottky diodes

Pd and Pt Schottky diodes on non-polar a-plane (11–20) GaN layers show large increases in both forward and reverse bias current upon exposure to 4% H2 in N2. The barrier height reduction due to hydrogen exposure is 0.11 eV for Pd/GaN and 0.14 eV for Pt/GaN, with long recovery times (>25 min) at room temperature. The sensitivity to hydrogen is significantly greater than for diodes on conventional c-plane (Ga-polar) GaN, but less than for c-plane (N-polar) material. The diode characteristics remain rectifying after exposure to hydrogen, unlike the case of N-polar GaN where Ohmic behavior is observed.