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 (H2) sensors both on a planar GaN film grown by Metal Organic Chemical Vapor Deposition and on a honeycomb GaN nanonetwork grown by Molecular Beam Epitaxy. The metal-semiconductor Pt/planar GaN film Schottky diode was fabricated and used as a H2 sensor element with response time τ of 80 s (10,000 ppm) and 2000 ppm limit of detection for hydrogen gas (LODH2) at 373 K. A significant improvement in H2 detection is observed for the honeycomb GaN nanonetwork. The characteristics of the H2 sensor on the honeycomb GaN nanonetwork are quantitatively studied in comparison with that on the planar GaN film. The response time τ 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 Ea from 6.22 to 2.4 kcal/mol. The reduced activation energyEa is regarded as the reason that leads to a superior H2 detection of the honeycomb GaN nanonetwork in terms of response time τ and operating temperature.