The Dependence of Transistor Parameters on the Distribution of Base Layer Resistivity

This paper presents a method of analyzing transistor behavior for any base-layer impurity distribution. In particular, expressions are derived for emitter efficiency ¿, transverse sheet resistance R, transit time ¿, and frequency cut-off f¿. The parameters ¿ and R are functions only of the total number of impurities in the base layer. The analysis is used to derive ¿, R, ¿ and f¿ for four different distributions-uniform, linear, exponential, and complementary error function. For each of these distributions a transistor base-layer design equivalent in R and f¿ is obtained. Comparison shows that for equivalent parameters the nonuniform distributions permit the use of wider base layers, but require greater maximum impurity concentrations and must be operated at high current densi