Effects of oxidation on band edge states in H-covered ultrasmall Si quantum boxes: Calculations of electronic states and oscillator strengths

Abstract

Electronic state calculations are performed by the extended Hückel-type nonorthogonal tight-binding method for a Si dihydride backbonded to oxygen on the hydrogen-covered (001) surface of ultrasmall Si 5×5×Nz (Nz=5,9,13, etc.) quantum boxes (QBs) with (100) planes. It is found that the backbond oxidation clearly induces surfacelike electronic states at the conduction-band edge and downshifts the band gaps. Calculated oscillator strengths in the oxidized QBs are about three orders of magnitude higher than those in the unoxidized counterparts, explaining luminescence enhancement due to oxidation observed in porous Si.