Perturbation analysis on large band gap bowing of dilute nitride semiconductors

摘要

Contrary to the conventional empirical law, band gap of dilute nitridesemiconductors decreases with nitrogen concentration. In spite of a number of investigations, origin of this "large band gapbowing", is still under debate. In order to elucidate this phenomenon, weinvestigate change of band edge energies of GaN$_x$As$_{1-x}$ due to nitrogenby using the perturbation theory. It is found that energy shift of conductionband edge is arising from mixing between $\Gamma$- and L-states and/or$\Gamma$- and X-states induced by displacement of Ga atoms around N. We alsofound that the valence band edge state shows upward shift in spite of negativepotential of nitrogen. These results are well understood from character of thewavefunctions and symmetry of the perturbation potential.