Published online by Cambridge University Press: 28 February 2011
We discuss how the geometrical irregularities of small crystallites, quantum dots or wires may play an essential role in the density of electronic states near the band gap in semiconductors. Assuming a possible irregular structure for porous silicon we show that the irregularity has a strong effect on the value of the band gap and of the density of states in the near band gap region. The effect of the irregularity is essentially to enhance the quantum confinement effect and to screen the fundamental wave-function from the surface.