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 Cl-2 plasma surface treated times are studied and demonstrated. The sensing behaviors are studied in terms of Schottky barrier height variation Delta(phi B), sensing response S-r, and transient-state response times. The highest sensing response (S-r) values of 7.1 x 10(4) and 2.12 x 10(5) are obtained in forward- and reverse-bias voltages, respectively, upon exposure to a 10,000 ppm H-2/air gas at 30 degrees C. In addition, a correspondingly large Schottky barrier height variation Delta(phi B) 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 Cl-2 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. (C) 2012 Elsevier B.V. All rights reserved.