DC thermal model of semiconductor device produces current filaments as stable current distributions

How current filaments arise in semiconductor devices can be studied with the aid of a simple two-dimensional thermal model. This dc model generates temperature and current distributions across the semiconductor chip. To use the model one must be able to prescribe the temperature dependence of the dc conductance in the chip from prior knowledge of the conduction mechanism. This model produces current filaments as stable current distributions. Moreover it demonstrates that current filaments will form in avalanche diodes at high power levels even if the chips are defect-free. The key to filament formation in a semiconductor device is an increase of the dc conductance with temperature at some operating point. In avalanche conduction, when the diode bulk leakage current increases faster than the avalanche current multiplication factor decreases with temperature, the avalanche conductance begins to rise. When this happens, a current filament forms raising the temperature locally to more than 1600°C, according to the model, and results in diode burnout. This mechanism is believed to be involved also in RF-induced burnout of avalanche diodes and in the burnout of other semiconductor devices.