Response Time of Semiconductor Photodiodes

The conventional phenomenological approach describes the response time of semiconductor photodiodes to short laser pulses as time required for collection of non-equilibrium carriers via processes of drift and diffusion. The effect of displacement currents due to dielectric relaxation of majority carriers in the charge-neutral region of semiconductor photodiode is usually neglected. This paper shows that dielectric relaxation of majority carriers may dominate the slow response of not fully depleted photodiodes and has to be taken into account for correct analysis of silicon photodiode response to a brief laser pulse. A phenomenological expression for the photodiode response time that accounts for the displacement current effects is proposed and used to compare with experimental results.