Improved hydrogen detection sensitivity of a Pt/Ga 2 O 3 /GaN diode

Abstract

ABSTRACT The Pt/Ga 2 O 3 /GaN diodes were fabricated in which the Ga 2 O 3 oxide layers were directly grown on GaN layer using a photoelectrochemical method. Then, the Ga 2 O 3 oxide films were annealed in O 2 ambiance at 700 o C for 2 hours to perform the E -Ga 2 O 3 crystalline phases. The hydrogen sensing character istics of Pt/GaN (metal-semiconductor, MS) and Pt/E -Ga 2 O 3 /GaN (metal-insulator-semiconductor, MIS) diodes under hydrogen-containing ambiance were studied in an air atmosphere. Compared with the MS devices, the MIS devices exhibited better hydrogen sensing ability. The result demonstrates that the E -Ga 2 O 3 layer plays an important role in the hydrogen sensing of the GaN based MIS diodes. Keywords: Ga 2 O 3 , GaN, hydrogen, MIS, sensors, diodes. 1. INTRODUCTION Much attention has been paid to the investigation of hydrogen detecting sensors recently due to the increase of hydrogen application in industry, especially due to its potential for using as a clean energy source. It is largely related to the fact that the hydrogen gas has the properties of spontaneous combustion and explosion at room temperature when the hydrogen concentration is more than 4% in air. Also, hydrogen atoms can penetrate into metals and affect the properties such as strength. It is necessary to keep the hydrogen content in the working ambient at a low level and hence the detection of hydrogen becomes more important with the development of hydrogen application. In 1975, Lundstrom et al. [1] reported the sensitivity of a Si-based sensor toward hydrog en gas. Long term stability and high temperature operation are important requirements for hydrogen gas sensors. But the sensors based on Si can not be operated above about 250