Electronic structure of "sequence mutations" in ordered GaInP2 alloys

The electronic consequences of layer thickness fluctuations in CuPt-ordered GaInP2 (layer sequence Ga-In-Ga-In...) are investigated. We show that the formation of a "sequence mutated" Ga-In-In-Ga...region creates a hole state h1 localized in the In-in double layer, while the electron state e1 is localized in the CuPt-ordered region. Thus, the system exhibits electron-hole charge separation in addition to spatial localization. This physical picture is preserved when the dimension of the mutated segment is reduced from 2D to 0D, resulting in disklike dot structures. Our theory explains the longstanding puzzle of the origin of the peculiar luminescence properties of ordered GaInP2.