Application of Hyperbolic Metamaterials for Responsivity Enhancement of Thin Film Photo-Conductive Detectors

A theoretical study on the application of periodically tapered metal-semiconductor layers on the top surface of a GaAs-based photo-conductive photodetector is performed and its influence on the absorbance and responsivity improvement is investigated. To do so, first, the proposed pyramid and cone-shaped hyperbolic metamaterial (HMM) structures consisting of periodic Au/GaAs layers are designed for the 820~840 nm which is the peak absorption wavelength of the thin-film photo-conductive layer. Based on the results around the structural parameters of HMMs, a proper structure is chosen to couple to the photo-conductive layer. The results of simulation in CST Microwave Studio show that the absorbance reaches near unity for the metasurface-enhanced detector and the responsivity enhancement of about 140 can be obtained by using pyramid-shaped structures. The results can be valuable for applications in different types of photodetectors.