Modeling of the disorder contribution to the band-tail parameter in semiconductor materials

In this paper, we present a quantitative and analytical formulation of the disorder contributions to the band-tail parameter model in semiconductor ma terials with Urbach exponential behavior, which arise from the influence of the bulk and grain boundary trap concentration and strain. We based our ca lculation on the Halperin-Lax model combined with a recent model that consi dered the tail parameter E-0 as the sum of interactive and disorder contrib utions. The resulting formulation converged to the Dow-Redfield model, whic h supports its validity. Our theory, applied to experimental data, yields b ulk-defect and grain-boundary trap concentrations in good agreement with re ports for mono- and polycrystalline semiconductors. Our model can describe wholly the band-tail parameter of any semiconductor. [S0163-1829(99)01924-4 ].