19 - Ga2O3-based gas sensors

Abstract

Recently, β-Ga2O3 has attracted much attention in gas sensing applications, especially at high temperatures and in harsh environments. Many researchers have demonstrated that β-Ga2O3 can serve as a reactive oxide layer, sensitive to a wide variety of gases at elevated temperatures. The gas sensing capability of β-Ga2O3 originates from surface reactions with gas molecules, which result in chemiresistive change in the conductivity. In this chapter, the β-Ga2O3-based gas sensors are reviewed. The crystal structure and surface atomic arrangement of β-Ga2O3 are first investigated with an emphasis on (2¯01) and (010) crystal orientations. The wet and dry etching characteristics of β-Ga2O3 are studied and the metal contact properties of both β-Ga2O3 single crystals are discussed. The gas sensing mechanism and the sensing characteristics of β-Ga2O3 are reviewed with respect to the detection of O2 and CO. Recent reports of β-Ga2O3-based hydrogen sensors are discussed, and the hydrogen sensing properties of (2¯01) and (010) β-Ga2O3 single crystals are compared.