A nanoscale metal-semiconductor-metal photodetector with a 40 nm-thick GaAs absorbing layer has been studied numerically and experimentally. A gold nanowire array is the top mirror of a Fabry-Perot cavity and forms interdigitated Schottky contacts. Nearly perfect absorption is achieved in TE polarization. It is shown numerically that the gold nanowire array induces light absorption in GaAs nanowires with tiny sections (100 nm × 40 nm). High external quantum efficiency (η > 40 %) is demonstrated.