Characterizations of AlGaN/GaN Membrane-type Photodetectors

Al0.12GaN/GaN membrane-type photodetectors (M-PD) were separated from the Si substrates through a chemical lift-off process. High photocurrent, low dark current, and high responsivity properties were observed in the M-PD structure compared to that on the Si substrate. Lattice-mismatch-induced tensile strain on the Al0.12GaN layer was enlarged in the M-PD structure and was analyzed by the photoluminescence and Raman spectra. From the simulation results, the energy band bending induced the potential barrier height at the AlN/air separated surface to deplete the surface states and suppress the leakage current. The strain in the AlGaN/GaN structures was manipulated by removing the Si substrate and roughening the AlN surface. The membrane-type ultraviolet photodetector consisted of the AlGaN/GaN two-dimensional electron gas channel and the large tensile strain at the Al0.12GaN layer, which can be used for high-efficiency optoelectronic applications.