HETEROBARRIER PHOTODIODE MSM STRUCTURES W ITH SUBPICOSECOND TEMPORAL RESOLUTION

Interdigital heterobarrier metal-semiconductor-metal (MSM) structures are proposed as ultrafast photodetectors of visible radiation. Vertica l photocarrier drift in MSM diode structures provides the simplest way of reducing the active region of a detector to the submicron size and of shortening considerably the response time without a significant lo ss of the radiation coupling-in efficiency. External electrooptic samp ling was used to determine the subpicosecond (half-amplitude duration 0.6 ps) electrical response of a detector built into a copolanar micro wave energy transmission line. Under a bias voltage of 1 V and for an optical excitation energy of 10 pJ per pulse the change in the photodi ode voltage amounted to 40% of the bias voltage, which makes these dio de structures sufficiently efficient and extremely fast detectors of o ptical radiation.