Transient Responses of The Majority and Minority Carriers During Rapid Reduction of The Inversion Charge in an MOS Structure

We studied in detail by TCAD simulation the transient behaviors, especially the carrier motions in the silicon, of a p-type MOS capacitor when a portion of inversion charge was discharged, with the investigated transient time spanning from 1 ps to 100 s. The excess inversion minority carriers (electrons) diffused from the silicon surface to the substrate during the transient. The majority carriers (holes) first flew in rapidly due to the reduced band bending within the dielectric relaxation time. Afterward, holes flew out to the substrate due to the overreaction of holes and the expansion of the depletion region. At the same time, holes also flew in to recombine with the excess minority carriers within the depletion region. As a result, the substrate hole current changed signs from positive to negative and finally positive.