A Strategic Review on Gallium Oxide Based Deep-Ultraviolet Photodetectors: Recent Progress and Future Prospects

High quality AlN epilayers were grown on sapphire substrates by metal organic vapor deposition and exploited as active deep ultraviolet (DUV) optoelectronic materials through the demonstration of AlN metal-semiconductor-metal (MSM) photodetectors. DUV photodetectors with peak responsivity at 200nm with a very sharp cutoff wavelength at 207nm have been attained. The AlN MSM photodetectors are shown to possess outstanding features that are direct attributes of the fundamental properties of AlN, including extremely low dark current, high breakdown voltage, and high DUV to visible rejection ratio and high responsivity. The results demonstrate the high promise of AlN as an active material for DUV device applications.

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200 nm deep ultraviolet photodetectors based on AlN

A General Strategy to Ultrasensitive Ga2O3 Based Self-Powered Solar-blind Photodetectors

Laser-induced graphene (LIG) is a simple, environmentally friendly, efficient, and less costly method, as well as can form various shapes on a flexible substrate in situ without the use of masks. More importantly, it can tune the work function of LIG easily by changing laser parameters to control the transportation of carriers. In this work, the work functions of LIG were controlled by adjusting the frequency or speed of the laser, and a series of LIG/GaOx Schottky photodetectors were formed. When the work function of the graphene increases, the Fermi energy is shifted below the crossing point of the Π and Π* bands, and then more electrons or holes can be activated to participate in the conduction process, resulting in low resistance. Meanwhile, a large built-in electric field can be formed when using a high work function LIG, which is more beneficial to separate photo-generated carriers. Enabled by the controllable LIG, LIG/GaOx Schottky photodetectors can be modulated to have high photoresponsivity or self-powered characteristics. Our work provides a high-performance photodetector with excellent mechanical flexibility and long-life stability, promising applications in the flexible optoelectronic fields.

Work function tunable laser induced graphene electrodes for Schottky type solar-blind photodetectors

Bandgap engineering of Gallium oxides by crystalline disorder

https://iopscience.iop.org/article/10.1088/1361-6463/abae36/pdf

Solar-blind photodetectors based on MXenes–β-Ga2O3 Schottky junctions

Solar-blind imaging based on 2-inch polycrystalline diamond photodetector linear array

Monoclinic Ga2O3 (β-Ga2O3) is a promising material for achieving solar-blind photodetection because of its unique characteristics, including its high breakdown electric field, radiation hardness, thermal and chemical stabilities, and intrinsic visible/solar-blind properties. Until now, several studies have investigated the development of high-performance β-Ga2O3 solar-blind photodetectors. However, these photodetectors can only detect the light intensity but not the light position. In this work, four-quadrant position-sensitive detectors (4Q-PSDs) were developed and demonstrated based on β-Ga2O3. 4Q-PSDs, comprising four identical metal-semiconductor-metal-structured photodetector components, demonstrate high uniformity, large signal-to-noise ratio, good ultraviolet/visible rejection ratio, and fast response/recovery time. Subsequently, the position of the illumination beam can be determined by analyzing the output signals of the four photodetector components. This work may indicate the promising application potential of the Ga2O3-based photodetectors in the fields of positioning, aligning, and monitoring the solar-blind beams.

Ga 2 O 3 solar-blind position-sensitive detectors

The quest for solar-blind photodetectors with outstanding optoelectronic properties and weak signals detection capability is essential for their applications in the field of imaging, communication, warning, etc. To date, Ga2O3 has demonstrated potential for high-performance solar-blind photodetectors. However, the performance usually decays superlinearly at low light intensities due to carrier-trapping effect, which limits the weak signal detection capability of Ga2O3 photodetectors. Herein, a Ga2O3 solar-blind photodetector with ultra-thin absorbing medium has been designed to restrain trapping of photo-generated carriers during the transporting process by shortening the carrier transport distance. Meanwhile, multiple-beam interference is employed to enhance the absorption efficiency of the Ga2O3 layer using an Al/Al2O3/Ga2O3 structure. Based on the ultra-thin absorbing medium with enhanced absorption efficiency, a 7 × 7 flexible photodetector array is developed, and the detectivity can reach 1.7 × 1015 Jones, which is among the best values ever reported for Ga2O3 photodetectors. Notably, the performance of the photodetector decays little as the illumination intensity is as weak as 5 nW/cm2, revealing the capacity to detect ultra-weak signals. In addition, the flexible photodetector array can execute the functions of imaging, spatial distribution of light source intensity, real-time light trajectory detection, etc. Our results may provide a route to high-performance solar-blind photodetectors for ultra-weak light detection.

Kaiyong Li

Papers

Bandgap engineering of Gallium oxides by crystalline disorder

Solar-blind photodetectors based on MXenes–β-Ga2O3 Schottky junctions

Solar-blind imaging based on 2-inch polycrystalline diamond photodetector linear array

Ga 2 O 3 solar-blind position-sensitive detectors

Ultra-sensitive flexible Ga2O3 solar-blind photodetector array realized via ultra-thin absorbing medium