Graphene–Coupled Highly Efficient THz Photomixer

A novel THz photomixer detector based on interdigitated multilayer graphene (MLG) on low-temperature-grown (LTG) GaAs is demonstrated. It exhibits an enhanced performance as compared with conventional LTG GaAs photomixers with metallic finger contacts. The obtained responsivity and the dynamic range are about 30$\times$ higher and the bandwidth is twice as large. The reason for this enormous improvement lies in the transparency of the graphene electrodes to VIS/NIR radiation which permits to optically excite mobile charge carriers in the LTG GaAs not only between the electrode fingers, but also below them. The measured enhancement of the detected photocurrent is explained by model calculations and simulations.