“…When the photodiodc is inverse biased with an appropriate saturating voltage, the current density in the intrinsic region is defined as (1) where e is the charge of an electron, n , and n,, are the volume densities of the electron and hole in the intrinsic region, and u, and u,, are the saturated velocities of the electron and hole, respectively 131. The total photocurrent from the photodiode is 1 Z ( t ) = -///j(r, t ) dr 1 , 0 ( C T = intrinsic region), (2) where L is the thickness of the intrinsic layer, and u denotes the entire intrinsic region. To obtain a current delay function due to the carrier transit time across the depletion region, the p-i-n photodiode is supposed to be exposed to a very sharp optical pulse of unit energy.…”