Absorption threshold frequency of silicon nanowires: Effect of cross section shape

In the present work, the influence of cross sectional shape on threshold frequency of absorption in Silicon nanowires is investigated. For this purpose, we have considered Silicon nanowires with three different cross-sectional shapes like square, circular and triangular. We have used the effective mass approximation to obtain energy levels and wave functions of the structures. We have obtained absorption threshold frequency for two different cases, constant and variable effective mass. In the latter case, we have calculated the mass of electron and hole as a function of cross section. Also, we have used the tight binding approximation to obtain energy levels and thereby absorption threshold frequency. The results show that: (i) the threshold energy frequency for triangular quantum wire is higher than the square and circular cases, (ii) the electron effective mass increases by increasing the cross section area and approach to bulk value for large cross section area.