Design calculations of reverse bias characteristics for microwave p-i-n diodes

The derivation of a set of design formulas for predicting the impedance of diffused p-i-n diodes as a function of reverse bias voltage is presented. The diode is divided into five regions, and appropriate approximations are made in each region to simplify the integration of resistive and reactive contributions to the total impedance. Using these formulas, curves of series resistance and capacitance versus voltage are computed for an experimental diode reported by Senhouse. The curves agree well with others obtained using more complicated methods of integration. In addition to being useful for design calculations, the formulas derived offer insight as to the effects of frequency on diode impedance and the relative contributions of the various regions of the diode to the total impedance.