Analysis of picosecond and subpicosecond MSM photodiodes with very low bias voltage

Recently, 4.8-ps FWHM current pulses were generated with a 10-μmm×15-μ GaAs metal-semiconductor-metal photodiode at a bias voltage of only 0.5 V. To explain this surprising result a full computer simulation was carried out to determine the pulse response as a function of the applied voltage. The simulations are in good agreement with the experiment and allow quantification of the contribution of various parameters to the pulse width. They also show that the photodiode can be used as subpicosecond sampling gate, even without the occurrence of a subpicosecond recombination mechanism, owing to the short diffusion relaxation time. A method is proposed for identifying the electron and hole currents in the photodiode by comparing the pulse response with the autocorrelation signal