Semipolar (112̅2) AlGaN-Based Solar-Blind Ultraviolet Photodetectors with Fast Response

Abstract

The high-quality semipolar (112̅ 2) AlGaN epitaxial films have been obtained on m-plane sapphire by metal−organic chemical vapor deposition. X-ray rocking curve measurements show the full-width at halfmaximums of semipolar (112̅ 2)-oriented AlGaN films are 0.357°and 0.531°a long [112̅ 3̅ ] AlGaN and [11̅ 00] AlGaN , respectively. The fabricated semipolar AlGaN metal−semiconductor−metal solar-blind ultraviolet (UV) photodetector (PD) exhibits a high responsivity of 1842 A/W. The fast response and reliability of the UV PD are ensured via fast switching with a rise and decay time of 90 ms and 53(720) ms, respectively. The UV PD exhibits a significant reduction in the dark current, that is, from 100 μA to 780 fA at 10 V, using a simple wet chemical etching to modify the surface properties of materials. The photo-to-dark-current ratio value of the etched UV PD reaches 4 orders of magnitude higher than the unetched UV PD under 270 nm illumination. These are attributed to the fact that KOH wet etching assists in eliminating the surface states and reconstructing the surface oxides. This work might provide a new potential for the development of solar-blind UV PDs with high performance.

High-Temperature Annealing Assisted High-Quality Semipolar (112̅2) AlN Film for Vacuum Ultraviolet Detectors

“…The evolution of the XRC-FWHMs for the AlN film is presented in Figure a. The crystalline quality of semipolar AlN with only 1 μm thickness in this work is much better than those nonpolar/semipolar AlN films in previous reports, as shown in Table . ,,− Based on the comprehensive XRD results and AFM analysis, it is noted that the original stripe morphology implies a large defect density and anisotropy. The appearance of large steps means that BSFs and PSFs are reduced along the [11̅00] AlN direction.…”

“…As the applied voltage increases, R further increases. The R of REG-AlN PD and DG-AlN PD are 2.23 and 1.33 A/W at 20 V, respectively, which are superior to the previous performance of VUV PD. , The external quantum efficiencies (EQEs) of REG-AlN PD are up to 25.3% at 10 V and 1 × 10 3 % at 20 V, respectively. From Figure c, it can be seen that the PDs have good repeatability in multiple optical on/off tests.…”

Multi‐Controllability of Ambipolar Photoconductivity in Transition Metal Dichalcogenides Van der Waals Heterostructures

“…In both operation modes, i.e., with and without the source‐drain bias V ds , the responsivity of our heterojunction PD under deep UV illumination are the highest among the reported PDs based on 2D materials and conventional semiconductors [ 25,41–44 ] (Table S1, Supporting Information). It is also comparable to the recently reported FePSe 3 /MoS 2 heterostructure PD at the same illumination wavelength (3.36 × 10 4 AW −1 at 265 nm at V ds = 4 V), [ 25 ] in which a gold back reflector was employed to enhance the light absorption at the heterostructure and shorten the transport distance of the photogenerated charge carriers.…”

“…A maximum responsivity of 140 mAW −1 is attained at V ds = 0 V that is higher than most of the reported UV PDs. [25,[41][42][43][44]…”

Horizontally‐Oriented Growth of Organic Crystalline Nanowires on Polymer Films for In‐Situ Flexible Photodetectors with Vis‐NIR Response and High Bending Stability

“…[59] The rise time mainly results from the transit time required for the photogenerated charge carriers to drift to the electrodes, while the fall time correlates with the transit time of electrons through electrodes as well as the trap states from the surface and internal defects. [60,61] Therefore, the long fall time suggests a high defect density existing on these nanowires after electrode deposition. In this work, these horizontally oriented nanowires are formed directly on a flexible surface through a one-step vapor-phase deposition.…”