Localization and percolation in semiconductor alloys: GaAsN vs GaAsP.

摘要: Tradition has it that in the absence of structural phase transition, or direct-to-indirect band-gap crossover, properties semiconductor alloys (bond lengths, band gaps, elastic constants, etc.) have simple and smooth (often parabolic) dependence on composition. We illustrate two types violations this almost universally expected behavior. First, at percolation composition threshold where a continuous, wall-to-wall chain given bonds (e.g., Ga-N-Ga-N...) first forms alloy $\mathrm{Ga}{\mathrm{As}}_{1\ensuremath{-}x}{\mathrm{N}}_{x}$), we find an anomalous behavior corresponding bond length Ga-N). Second, show if dilute $\mathrm{Ga}{\mathrm{As}}_{1\ensuremath{-}x}{\mathrm{N}}_{x}$ for $x\ensuremath{\rightarrow}1$) shows localized deep impurity level gap, then there will be domain concentrated its electronic optical bowing coefficient) become irregular: unusually large dependent. contrast with weakly perturbed system $\mathrm{Ga}{\mathrm{As}}_{1\ensuremath{-}x}{\mathrm{P}}_{x}$ having no gap levels limits, behaves normally case.