Modeling carrier trapping at semiconductor/dielectric interfaces based on first-principles calculations of nonradiative capture

We demonstrate a quantitative framework to evaluate a nonradiative capture process with multiphonon emission in a semiconductor/dielectric heterostructure, mediated by a tunneling process. In addition to evanescent tunneling decay, the presence of an internal electric field modifies the relative energy depth of the carrier trap depending on the distance, modulating the overall capture behavior. We quantitatively derive the capture rate based on the parameters of the device structure (gate voltage, threshold voltage, dielectric material thickness, and temperature). We benchmark the formalism for the case of a Si/SiO2 heterostructure, using an isolated Si dangling bond in α-quartz as a prototype defect in silica. We find that the calculated capture coefficients show a nonmonotonic trend as a function of distance of the defect from the interface, due to countervailing trends in capture barrier and wave-function decay. The predicted capture rates are in reasonable agreement with experimentally measured capture time constants, showing promise for the application of this compact model.