Metal-semiconductor-metal electron detectors

Abstract

Metal-semiconductor-metal (MSM) junctions are a standard photon detector for high-speed applications due to fast response time (subpicosecond) and long device lifetime, high gain (QE>100%), small device area, and reduced capacitance per area. Here, the authors characterize how such devices perform as electron detectors, performing preliminary gain and frequency response experiments on MSM illuminated by an electron beam. Experiments were performed on both a Hitachi scanning electron microscope SEM 2500, and in a custom-made vacuum system used as a testbed for analog to digital conversion. The experiments demonstrated a gain of 300× at 5 kV acceleration voltage and frequency response up to 0.85 GHz, which complied with the specifications required by the analog to digital converter. Using other semiconductor materials (GaAs) as well as e-beam lithography to define smaller fingers will lead to faster response times.