Transient Response of a p-n Junction

The authors investigate the transient response of a p-n junction in a circuit where the applied voltage is suddenly switched from the forward to the reversed direction. The behavior is studied as a function of the circuit resistance. The solution of the appropriate diffusion equation is carried out for a time-dependent boundary condition, resulting in an integrodifferential equation. Analytical and numerical results for the current and the junction voltage as a function of time are then obtained by suitable approximations for the ``recovery'' and reverse periods. The ``recovery'' or reversal time tf is the time required for the junction voltage to become negative and is given by erftfτ=11+(If/Ir),where τ is the lifetime of holes, If is the forward current, and Ir the initial reverse current, which is limited by the external resistance.