AlGaN UV Detector with Largely Enhanced Heat Dissipation on Mo Substrate Enabled by van der Waals Epitaxy

Abstract

The epitaxy of AlGaN on metallic substrates exhibits numerous advantages including flexibility, vertical carrier injection, and enhanced heat dissipation for optoelectronic devices; however, there are still many challenges for the growth of AlGaN according to the serious interfacial reaction and lattice mismatch by conventional epitaxial techniques. In this work, the c-oriented AlGaN is grown on polycrystalline Mo substrate by van der Waals (vdWs) epitaxy with graphene as the insertion layer. A hightemperature annealed AlN is deposited as the nucleation layer, which optimizes the crystalline quality of following AlGaN. The isolation effect of the graphene insertion layer results in a good epitaxial interface, which suppresses the atoms diffusion and chemical reaction, demonstrating by the theoretical calculation of high energy barriers for Al/Mo atoms penetrating through graphene insertion layer. The ultraviolet (UV) detector is fabricated by further growing a n-AlGaN layer as the photosensitive absorber, whose responsivity (1.7 × 10 −3 A W −1 ) is comparable with that fabricated on conventional sapphire. Even better, the UV detector on the Mo substrate possesses enhanced heat dissipation ability due to its higher thermal conductivity, and the temperature elevation after consistently applying a drive voltage largely decreases by 50%. This work enlightens the growth of AlGaN materials and fabrication of high-power/high-voltage optoelectronic devices on polycrystalline metallic substrates by the mean of vdWs epitaxy.

Deep Ultraviolet Photodetector: Materials and Devices

“…Ultrafast UV photodetectors based on AlGaN were successfully developed with an MSM structure [88], the response time and low dark current of which were less than 25 ps and 20 pA, respectively. C-oriented AlGaN grown on polycrystalline Mo substrate was also used as a DUV detector, the temperature effect of which could be decreased by 50% under high drive voltage [89]. AlGaN p-i-n photodetectors composed of junctions with opposite doping types have been widely explored because it is feasible to optimize their quantum efficiency and response speed by tailoring their depletion layer thickness (the intrinsic layer).…”