Physical phenomena in Si power diodes operating at high carrier injection levels and high temperature

The physics of fast recovery 3.3 kV Si power diodes radiation induced recombination centers operating under forward bias at large current densities and high temperatures have been studied both experimentally and by means of computer simulations. In the experimental studies the dynamic I-V characteristics, the surface temperature and the surface potential distribution in the n-base have been measured, while the diodes were being subjected to single 1.3 ms half-sine-wave current pulses having a density in the range of 100 to 7200 A/cm². The experimental dynamic I-V characteristic curves obtained are rich in features and determined by the effects that temperature and carrier concentration have on the carrier mobility and lifetime, on the Fermi-Dirac distribution function and on the energy band gap. The experimental results have been used to check the validity of the physical models implemented in the simulation package AVANT! MEDICI. Simulations performed using the standard physical models implemented in MEDICI give an excellent agreement with measurement results up to a peak current density of 1500 Amps/cm², and a reasonable good one up to a peak current density of 2000 Amps/cm². However, the agreement between measurements and simulations is very poor at peak current densities above 2000 Amps/cm²