Effects of surface states on hydrogen sensing performance of Pt-GaN Schottky diodes

Effects of surface states on hydrogen sensing performance of Pt-GaN Schottky diodes were investigated. First, hydrogen sensing characteristics of Pt-GaN Schottky diodes fabricated on as-grown and annealed GaN surfaces are studied in order to investigate the correlation between the surface defects of GaN and hydrogen sensing performance. As a result, significant differences of the sensitivity among the devices were not observed, indicating that surface defects of GaN do not play a critical role in hydrogen sensing characteristics of Pt-GaN Schottky diodes. Second, influence of dielectrics between Pt and GaN surface was studied. In consequence, Pt-GaN diodes with 10nm SiO2 dielectric between Pt and GaN surface, deposited by RF sputtering, show the dramatic improvement of the hydrogen detection sensitivity, which is twice higher than for conventional Pt-GaN Schottky diodes. By sharp contrast, Pt-GaN diodes with 10nm SixNy dielectric, deposited by RF sputtering, do not show any response to hydrogen. These results suggest that dielectrics between metal and semiconductor are much more important than surface defects in hydrogen sensing performance. (C) 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.