title: Size-Dependence of Acceptor and Donor Levels of Boron and Phosphorus Codoped Colloidal Silicon Nanocrystals.
abstract: Size dependence of the boron (B) acceptor and phosphorus (P) donor levels of silicon (Si) nanocrystals (NCs) measured from the vacuum level was obtained in a very wide size range from 1 to 9 nm in diameter by photoemission yield spectroscopy and photoluminescence spectroscopy for B and P codoped Si-NCs. In relatively large Si-NCs, both levels are within the bulk Si band gap. The levels exhibited much smaller size dependence compared to the valence band and conduction band edges. The Fermi level of B and P codoped Si-NCs was also studied. It was found that the Fermi level of relatively large codoped Si-NCs is close to the valence band and it approaches the middle of the band gap with decreasing the size. The results suggest that below a certain size perfectly compensated Si-NCs, that is, Si-NCs with exactly the same number of active B and P, are preferentially grown, irrespective of average B and P concentrations in samples.
authors.affiliation: Department of Electrical and Electronic Engineering, Graduate School of Engineering, Kobe University , Rokkodai, Nada, Kobe 657-8501, Japan.
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Hori
authors.affiliation: Department of Electrical and Electronic Engineering, Graduate School of Engineering, Kobe University , Rokkodai, Nada, Kobe 657-8501, Japan.
authors.forename: Shinya
authors.initials: S
authors.lastname: Kano
authors.affiliation: Department of Electrical and Electronic Engineering, Graduate School of Engineering, Kobe University , Rokkodai, Nada, Kobe 657-8501, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Sugimoto
authors.affiliation: Department of Electrical and Electronic Engineering, Graduate School of Engineering, Kobe University , Rokkodai, Nada, Kobe 657-8501, Japan.
authors.forename: Kenji
authors.initials: K
authors.lastname: Imakita
authors.affiliation: Department of Electrical and Electronic Engineering, Graduate School of Engineering, Kobe University , Rokkodai, Nada, Kobe 657-8501, Japan.
authors.forename: Minoru
authors.initials: M
authors.lastname: Fujii
keywords: Fermi level; HOMO; LUMO; Silicon; acceptor level; codoping; donor level; doping; impurity; nanocrystal; quantum dot; size dependence