A regional approximation for a real p+–i–n+ double-injection structure by including both diffusion and space charge effects

Abstract

On the basis of the regional approximation method a new model description is represented for double injection in the high resistivity i region of a sandwiched p+‐i‐n+ structure, containing a monoenergetic set of acceptor‐like deep traps completely filled in the thermal equilibrium. The injecting contacts are semiconducting p+ and n+ regions forming two usual homojunctions with the active i region. The barrier‐ and volume‐controlled current flow in the forward biased p+‐i‐n+ diode is calculated by taking into account both diffusion and space charge effects, but no effects of thermal carriers within the i region. An approximative analytical description of the current‐voltage characteristic including the threshold voltage for the onset of the negative differential resistance regime is given. The results of the model calculations are valid within a certain current range and above a certain critical length of the i region. The threshold voltage is a product of a modified Lampert threshold voltage where the length 2L of the i region is replaced by a reduced length 2L* describing the influence of diffusion effects in the neighbourhood of the p+‐contact, and of a factor which depends on the ratio of the hole and electron mobilities, on the ratio of the hole lifetimes for high and low injection conditions, and on the quotient of a dielectric relaxation time for the holes and of the low injection lifetime for the holes.