V-Band InP DDR IMPATTs for High Current Operation

Simulation studies have been carried on the DC and Small Signal properties of DDR (Double Drift region) Indium Phosphide IMPATT diode at high bias current level at 60 GHz. A double iterative computer method based on drift diffusion model has been used for our study. The bias current density has been varied from 0.5x10⁸A/m² to 10x10⁸A/m². The result shows that as we increase the bias current density, avalanche region becomes wider due to more space charge accumulation near the junction in the avalanche region. This behavior is shown in the E-Field vs. distance profile where the E-field gradually becomes flatter near the junction instead of sharp fall after a bias current density of 3 x 10⁸A/m2 and thus approaches a p-i-n diode. Hence, the negative resistance obtained from the drift region which is mainly responsible for power generation becomes smaller than the resistance from the avalanche region. So, the efficiency also decreases after a bias current density of 3x10⁸A/m² from 16.63% at 0.5x10⁸A/m² to 3.8% at 10x10⁸ A/m² bias density.