Phonon-assisted tunneling and interface quality in nanocrystalline Si/amorphous SiO2 superlattices

We report on the interface quality and phonon-assisted tunneling in nanocrystalline Si (nc-Si)/amorphous SiO2 (a-SiO2) superlattices (SLs) prepared by magnetron sputtering and thermal crystallization of nanometer-thick a-Si layers. Phonon-assisted tunneling is observed in a bipolar nc-Si based structure, which confirms that the nc-Si/a-SiO2 junction is not only abrupt but also nearly defect free. The conclusion is supported by capacitance–voltage measurements from which the estimated interface defect density is found to be ∼1011 cm−2 for an eight-period SL. Such high quality interfaces hold considerable promise for the development of nc-Si SL quantum devices.