Space-charge-influenced avalanche-breakdown characteristics: an improved approximation

The space-charge effect in millimetre-wave avalanche transit-time diodes is investigated. It is shown that for high current densities and especially for diodes punched through at breakdown, the well known space-charge resistance expression is not in accordance with the I/V data measured under pulse conditions. By introducing the effective doping approximation, the measured characteristics can be explained. An expression for a current-density-dependent space-charge resistance is proposed.