Space charge and thickness dependent dc electrical breakdown of solid dielectrics

A new model based on space charge dynamics under very high dc electric field has been proposed to explain thickness dependent dielectric breakdown. Space charge phenomenon under high electric field has been studied for several decades thanks to the development of new charge mapping techniques. Overwhelming evidences show that the charge packet can be formed in the material under high electric field. The formation and dynamics of the charge packet will result in local electric field enhancement that has a direct impact on breakdown. It has been found that the key factors leading to the formation of charge packet are negative differential mobility and low trapping coefficient. Take these factors into the space charge based model, our simulation results clearly show that the breakdown is dependent on the sample thickness. Through the simulation, it has been noticed that the electrical breakdown field reduction depends on several parameters such as the onset of critical electric field when breakdown occurs. By varying the ramp rate of dc applied voltage, simulation has also shown that the breakdown strength increases with the voltage ramp rate.