A Highly Sensitive Hydrogen Sensor Based on Pd/Ga₂O₃/AlGaN/GaN Schottky Diode

Abstract

A Pd/Ga ₂ O ₃ /AlGaN/GaN Schottky-diode hydrogen sensor with high sensitivity is fabricated and investigated. For the coating of a wide energy-gap Ga ₂ O ₃ sensing metal oxide layer on AlGaN/GaN structure, the Schottky barrier height can effectively lower when hydrogen gas is injected. Attributed to a two-dimensional electron gas (2DEG) at AlGaN/GaN heterojunction and large barrier-height changes, it exhibits high current variation and good sensing capability. Experimental results show that a maximum sensing response ratio S _R up to 3.19 × 10 ⁷ is achieved under 1% H ₂ /air at 343K and applied voltage of 0.56 V, which is higher than those of the previous reports. At applied voltage of 0.6 V, the S _R values decrease from 4.48 × 10 ⁶ to 591 under 1% H ₂ /air as temperature increases from 343K to 493K. In addition, a low detection level is of 1 ppm H ₂ /air, providing a wide hydrogen concentration sensing range (1 ppm ∼ 1% H ₂ /air). For the simple structure, high sensing response, wide sensing range, and high temperature operation durability, the studied device is very suitable for application on hydrogen detection.