Growth of Sn-Doped β-Ga2O3 Nanowires and Ga2O3−SnO2 Heterostructures for Gas Sensing Applications

Abstract

Although β-Ga2O3 thin films and nanowires (NWs) show promise as very stable and reliable active components for high temperature gas sensors, their use at room temperatures is limited due to poor electrical conductivity. To address this problem, we grew Sn-doped β-Ga2O3 nanowires by the vapor−liquid−solid (VLS) approach. Sn-doped β-Ga2O3 NWs with diameters of 100−250 nm retained the monoclinic β-Ga2O3 structure, though photoluminescence (PL) emission was red-shifted by up to 50 nm relative to the deep defect band typically observed for pure β-Ga2O3 NWs. When higher amounts of Sn were introduced, individual Ga2O3−SnO2 heterostructures (HS) self-assembled, to form three distinctive parts: monocrystalline Sn-doped β-Ga2O3, poorly crystalline Sn-doped β-Ga2O3, and polycrystalline Ga-doped SnO2, thus realizing a p-n junction within a single HS. Factors responsible for the self-assembly of Ga2O3−SnO2 HS are the different vapor pressures of Sn and Ga and different growth kinetics of Ga2O3 and SnO2. Inhomogeneity ...