Comparative study of Schottky diode type hydrogen sensors based on a honeycomb GaN nanonetwork and on a planar GaN film

We demonstrate Schottky diode type hydrogen (H-2) sensors both on a planar GaN film grown by Metal Organic Chemical Vapor Deposition and on a honeycomb GaN nanonet-work grown by Molecular Beam Epitaxy. The metal-semiconductor Pt/planar GaN film Schottky diode was fabricated and used as a H-2 sensor element with response time tau of 80s (10,000 ppm) and 2000 ppm limit of detection for hydrogen gas (LODH2) at 373 K. A significant improvement in H-2 detection is observed for the honeycomb GaN nanonetwork. The characteristics of the H-2 sensor on the honeycomb GaN nanonetwork are quantitatively studied in comparison with that on the planar GaN film. The response time tau is shortened by a factor of 27 (3 s versus 80 s) and the LODH2 is lowered by two orders of magnitude, from 2000 to 50 ppm. Moreover, the operating temperature could be reduced to room temperature. Through analyzing the transient-state, we observed a reduction of activation energy E-a from 6.22 to 2.4 kcal/mol. The reduced activation energyE(a) is regarded as the reason that leads to a superior H-2 detection of the honeycomb GaN nanonetwork in terms of response time tau and operating temperature. Copyright (C) 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.