Electronic states and optical transitions in small Si quantum boxes

Abstract

Electronic and optical properties of small Si quantum boxes (QBs) with hydrogen saturators (referred to as a N x × N y × N z structure, where N x , N y and N z are the number of Si monolayers along the [100], [010] and [001] directions, respectively) are studied using the extended Hückel-type nonorthogonal tight-binding method. It is found that a clear transition between the bulk-like and surface-like conduction band (CB) edge states takes place alternately by changing N z , among others, in the 5×5× N z ( N z =5,7,9,…) QBs, resulting in an oscillation behavior in band gap and oscillator strength. The occurrence of the surface-like CB edge state, which is responsible for the enhanced oscillator strength, is found to be ascribed to an inter-hydride interaction between the trihydride units at the side of the (00 1 ̄ ) surface.