An analytical model for depletion-region capacitance and widths of diffused p-n junctions

Abstract

FAT DUEN HOtDepletion region widths and capacitance for silicon diffused p-n junctions with gaussian and complementary-error-function profiles have been calculated in detail by using an earlier model for depletion capacitance of an exponentialconstant p-n junction. Beyond a certain range linear graded approximation is used to obtain better results. Incorporating graded junction approximation into the capacitance model an analytical model has been formulated which is valid for broad ranges of voltage, junction depth, background doping and surface concentration. Using this analytical model depletion capacitance and total widths of diffused junctions can be estimated from a set of expressions. Therefore, it is a viable alternative to the Lawrence and Warner curves which have been widely used in integrated circuit design. Furthermore, this analytical model has been simplified. This simplified model can be used to calculate depletion-region widths and capacitance for given values of applied voltage, junction depth, background impurity concentration and surface concentration by hand calculation. The results obtained here can readily be extended to other semiconductor materials.