A new metal-semiconductor-metal photodetector (MSM-PD), which is incorporated with coplanar striplines on high resistivity GaAs and has ultrahigh speed, is proposed and investigated experimentally as well as theoretically. A photocurrent gain over 50 has been observed at low frequency. In the high frequency region, the flat primary photocurrent response up to 1.5 GHz was obtained and the switching speed less than 100 ps was observed for GaAlAs laser pulses. Potentiality for detecting picosecond pulses is predicted. Photoresponse is almost flat in the wavelength region from 0.45 µm to 0.87 µm.
Applications of MSM-PDs to optoelectronic logic circuits, such as AND gate and INHIBITOR, are demonstrated at less than 200 ps switching speeds.