Temperature-dependent properties of Pd/GaN Schottky type hydrogen sensors with Cl2 plasma surface treatments

Temperature-dependent hydrogen sensing properties of Pd/GaN Schottky type sensors with different Cl2 plasma surface treated times are studied and demonstrated. The sensing behaviors are studied in terms of Schottky barrier height variation ΔφB, sensing response Sr, and transient-state response times. The highest sensing response (Sr) values of 7.1 × 104 and 2.12 × 105 are obtained in forward- and reverse-bias voltages, respectively, upon exposure to a 10,000 ppm H2/air gas at 30 °C. In addition, a correspondingly large Schottky barrier height variation ΔφB of 0.38 eV is found. This could be attributed to the effective dissociation of hydrogen molecules due to a rougher Pd surface and lower baseline current. Moreover, the studied devices with Cl2 plasma surface treatment have a stable and widespread reverse voltage operation regime. From transient-state behaviors measurement, the studied device with a 30 s plasma surface treatment shows the overshooting phenomenon and fast response (recovery) time of 4 (5) s.