Enhanced Ultraviolet Detection by Constructing Ga2O3/TiO2 Heterojunction Photodiode Featuring Weak Light Signal Sensing

In this article, a deep-ultraviolet (DUV) photodetector (PD) based on a Ga2O3/TiO2 planar heterojunction is fabricated by both the solution and the metalorganic chem- ical vapor deposition (MOCVD) methods. The DUV PD demonstrated a range of impressive DUV sensing properties, such as an ultrahigh responsivity ( $R$ ) of 275 A/W, a large spec- ific detectivity ( $D^{\ast}$ ) of $6.69\times 10^{{16}}$ Jones, and an external quantum efficiency (EQE) of $1.35\times 10^{{5}}$ under illumination with a light intensity of $0.1~\mu \text{W}$ /cm2 at 5 V. The results indicated that the PD had a capacity for weak DUV light signal sensing along with high performance, suggesting high sensitivity. In addition, the DUV PD can operate stably in a self-powered mode. The excellent performance of the DUV PD comes from the creation of the built-in electric field in heterojunction and the dual absorption of DUV light both by the Ga2O3 layer and TiO2 layer. In all, the achievements in this work may promote the application of sensitive Ga2O3-based optoelectronics in energy-conserving DUV sensing systems.