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

Abstract

This paper presents a method of analyzing transistor behavior for any base-layer impurity distribution. In particular, expressions are derived for emitter efficiency γ, transverse sheet resistance R, transit time t, and frequency cut-off f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">α</sub> . The parameters γ and R are functions only of the total number of impurities in the base layer. The analysis is used to derive γ, R, t and f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">α</sub> 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 <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">α</sub> 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