Low-field transport in SiO2

Low-field electronic transport trends in silicon dioxide (SiO2) are usually rationalized in terms of a mobility that is established by the rate of carrier (electron or hole) scattering. However, this perspective leads to a dilemma in which the hole mean free path in SiO2 is inferred to be much less than the interatomic spacing. An alternative picture is proposed herein in which electronic transport in an amorphous insulator such as SiO2 is diffusive (as exemplified by Brownian motion) and primarily involves carrier trapping, rather than scattering. Within this framework, electron transport in SiO2 is found to be a non-equilibrium, diffusive process with negligible trapping, whereas hole transport in SiO2 is dominated by quasi-equilibrium trapping. Non- or quasi-equilibrium behavior are distinguished by the relative magnitude of the carrier drift length compared to the SiO2 thickness, or equivalently, by the transit time compared to the carrier capture (trapping) time.