Doping dependence of second breakdown in a p-n junction

The delay time before the onset of second breakdown was measured at the collector-base junctions of four types silicon n-p-n planar transistors. The dependence of delay time on input power was found to obey a relationshiop of the form pτⁿ = constant. The value of n increased slightly, and the value of the constant decreased, with decreasing collector doping. For all four types of transistors, n was close to 0.5, and when a curve of the form pτ ^{1 2} = constant was fitted to the experimental data, the constant could be related to the temperature at which the collector impurity concentration becomes equal to the intrinsic carrier concentration.