Investigation of the switching behavior of pin-diodes using electronic analog models

An electronic analog model simulating the behaviour of diodes with pin-structure switched from forward to reverse bias is presented. Diodes with a lightly doped middle-region are used as power rectifiers, microwave modulators and step recovery diodes. Under the assumption of high injection and neutrality, the differential equations of the electrons and holes in the middle-region can be represented by a resistance-capacitance network. The conditions at the two boundaries ot the middle-region during the forward and storage period are simulated by constant current sources at the borders of the network. After the storage period the space-charge region of the pi-junction and somewhat later the space-charge region of the in-junction extend reducing the neutral part of the middle-region. This effect is simulated in the analog model by shortening the RC-network piece by piece. The currents at the moving borders of the network are reduced similar to the decreasing diode current during the decay period. Using this analog model the reverse recovery process of diodes with arbitrary doping profiles in the middle-region can be investigated. The model yields terminal properties and some quantities in the interior of the device, such as carrier densities and particle currents, as function of position and time. Results on the influence of forward and reverse currents, doping profile, width and carrier-lifetime in the middle-region are reported.