Deep-Uv Wavelength-Selective Photodetectors Based On Lateral Transport In Algan/Aln Quantum Well And Dot-In-Well Structures

We report on the development of deep-ultraviolet (DUV) wavelength-selective top-illuminated photodetectors based on AlGaN/AlN quantum-dots-in-wells. Structures consisting of 100 AlGaN wells and AlN barriers were grown by plasma-assisted molecular beam epitaxy on sapphire substrates. Interdigitated metal-semiconductor-metal photodetector devices were formed lithographically using indium as the contact metal. The effect of variation of the group III to group V flux ratio and the use of indium as a surfactant on the UV photoresponse were determined. Growth under near-stoichiometric conditions lead to a photocurrent peak in the 210-215 nm range with a peak width of similar to 20 nm, with no other additional signatures in the entire UV-visible range. Under excess group III conditions, a second redshifted peak was observed at similar to 225 nm with significantly (up to 10x) higher responsivity. This enhancement was linked to the formation of quantum dots with truncated pyramidal structures with near-uniform size distribution and density of 6 x 10(10) cm(-2) within the quantum wells. Their formation was attributed to the process of droplet epitaxy. Such photodetectors do not require p-type doping or growth onto UV-transparent substrates and are appropriate for monitoring DUV skin-safe germicidal radiation in the presence of ambient visible light. (C) 2021 Author(s).