Functional modeling of integrated injection logic—Transient analysis

A transient analysis of integrated-injection logic I
²
L structures is presented. This analysis is based on calculating the different depletion and neutral region charges. Doping profile, high-level effects, and geometrical layout are taken into account. To formulate a transient functional model of the structure, regional transient delays are defined as ratios of the corresponding charges to the electron current density J
n
of the n-p-n vertical transistor. An analytical expression is given for the dominant storage time; τ
epi
. The ratio of the stored charges in a metal-covered and oxide-covered base region is related to the surface recombination velocity and the ratio of the corresponding current densities. In a partitioned CAD model (as in Berger's injection model), the regional transient delays are expressed in terms of the corresponding current densities rather than J
n
. The computed results for a five-state ring oscillator are compared to measurements.