A general strategy to ultrasensitive Ga2O3 based self-powered solar-blind photodetectors

Ga2O3 based self-powered photodetectors, which can work in photovoltaic mode, show great potential applications in the next-generation photodetectors. Due to the difficulty of p-type doping of Ga2O3, constructing heterojunctions is a promising alternative for self-powered Ga2O3 photodetectors. Although several inorganic materials have been focused on fabricating Ga2O3 based heterojunction, some disadvantages prevent them from being widely used, such as the large lattice mismatch, the unsuitable bandgap, the inflexibility, the complex preparation process, etc. In this study, a general strategy has been proposed for high-performance photodetectors through building a type-Ⅱ Ga2O3 heterojunction with the small-molecule hole transport materials (SMHTMs). The relatively large hole mobility of SMHTMs guarantees the high-speed transport of the photogenerated holes, and the solar-blind filter effect of the SMHTMs films makes the photodetector highly spectrum selective. Herein, four types of SMHTMs have been used to constructed photodetectors with Ga2O3, and all of them exhibit self-powered characteristics with Ion/Ioff ratios of about>105, which is 1–2 orders of magnitude larger than these previously reported Ga2O3 photodetectors. Among them, the photodetector based on β-Ga2O3/TAPC heterojunction shows the best photoelectrical performances with a dark current of about 20 fA, a Ion/Ioff ratio of 5.9 × 105, and a detectivity of 1.02 × 1013 Jones at 0 V, all of which are amongst the best values ever reported for Ga2O3 based self-powered photodetectors. The high-speed transport of the photogenerated holes and large built-in field in the β-Ga2O3/SMHTMs heterojunctions should be responsible for these remarkable performances. This work provides a feasible strategy to high-performance Ga2O3 based self-powered photodetectors, thus may push forward their applications.