A method of determining impurity diffusion coefficients and surface concentrations of drift transistors

摘要

In order to control the electrical parameters of drift transistors, it was found necessary to control the impurity concentration gradient in the base. An extension of the space charge widening theory provides a method of calculating this gradient, the surface concentration, and the diffusion coefficient. By this method, the diffusion coefficient of arsenic into germanium at 725°C was found to be3 times 10^{-12}cm2/sec, and the initial surface concentration was of the order of 1021atoms/cm3. Universal graphs for design calculations and rapid reference are presented.