Review of polymorphous Ga2O3 materials and their solar-blind photodetector applications

Light detection in the deep-ultraviolet (DUV) solar-blind waveband has attracted interest due to its critical applications, especially in safety and space detection. A DUV photodetector based on wide-bandgap semiconductors provides a subversive scheme to simplify the currently mature DUV detection system. As an ultra-wide-bandgap (4.4-5.3 eV) semiconductor directly corresponding to the DUV solar-blind waveband, Ga2O3 has an important strategic position in the prospective layout of semiconductor technology owing to its intrinsic characteristics of high breakdown electric field, excellent tolerance of high/low temperature, high resistance to radiation, and rich material systems. As the only native substrate that can be fabricated from melt-grown bulk single crystals, beta-Ga2O3 has attracted a lot of attention both in power-electronic and photo-electronic devices. In addition, other metastable phases (e.g. alpha, epsilon, gamma) of Ga2O3 have attracted great interest due to their unique properties. In this work, we discuss the advances in achieving bulk and film Ga2O3 materials with different crystal phases. In addition, the latest achievements with polymorphous Ga2O3-based solar-blind photodetectors (SBPDs) and the methods to enhance their performance, including doping, annealing, and transparent electrodes, are also discussed. Furthermore, as the most desirable application, DUV imaging technologies based on Ga2O3 SBPDs are systematically summarized. Finally, conclusions regarding recent advances in Ga2O3 SBPDs, remaining challenges, and prospects are presented and discussed.