The investigation of electrical and optical properties of micro-scale AlGaN deep ultraviolet (DUV) light-emitting diodes (LEDs) emitting at ∼ 275 n m was carried out, with an emphasis on fabricated devices having a diameter of 300, 200, 100, 50, and 20 µm, respectively. It was revealed that the LED chips with smaller mesa areas deliver considerably higher light output power density; meanwhile, they can sustain a higher current density, which is mainly attributed to the enhanced current spreading uniformity in micro-scale chips. Importantly, when the diameter of LED chips decreases from 300 µm to 20 µm, the peak external quantum efficiency (EQE) increases by 20%, and the EQE peak current density can be boosted from 8.85 A / c m 2 and 99.52 A / c m 2 . Moreover, we observed a longer wavelength emission with enlarged full-width at half-maximum (FWHM) in the LEDs with smaller chip sizes because of the self-heating effect at high current injection. These experimental observations provide insights into the design and fabrication of high-efficiency micro-LEDs emitting in the DUV regime with different device geometries for various future 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, Ga ₂ O ₃ 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, β -Ga ₂ O ₃ has attracted a lot of attention both in power-electronic and photo-electronic devices. In addition, other metastable phases (e.g. α, ϵ, γ ) of Ga ₂ O ₃ have attracted great interest due to their unique properties. In this work, we discuss the advances in achieving bulk and film Ga ₂ O ₃ materials with different crystal phases. In addition, the latest achievements with polymorphous Ga ₂ O ₃ -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 Ga ₂ O ₃ SBPDs are systematically summarized. Finally, conclusions regarding recent advances in Ga ₂ O ₃ SBPDs, remaining challenges, and prospects are presented and discussed.