Excitation and de-excitation properties of silicon quantum dots under electrical pumping

In this work, the stationary and time-resolved electroluminescence (EL) properties of Si quantum dots embedded within a metal-oxide-semiconductor device are investigated. In particular, we measured the excitation cross section of Si nanocrystals under electrical pumping, finding a value of 4.7E-14 cm2 which is two orders of magnitude higher with respect to the excitation cross section under 488 nm optical pumping. We also studied the radiative and nonradiative decay processes occurring in these devices by measuring the time evolution of the EL signal. We demonstrate that the mechanism responsible for the emission is the same under both electrical and optical pumping. The overall quantum efficiency of the electrical pumping is estimated to be two orders of magnitude higher than the quantum efficiency for optical pumping in all the studied temperature ranges.