An intrinsic formation mechanism for midgap electronic statesin semiconductor glasses

摘要

We argue that semiconducting quenched liquids and frozen glasses may exhibit a set of peculiarelectronic states of topological origin. These states reside at strained regions arising during structuralreconfigurations between distinct aperiodic states intrinsic to quenched melts. The strained regionsare domain walls separating the distinct aperiodic states; their number is about 1020 cm~(-3)in allglassformers owing to the universal dynamics of deeply supercooled melts. Even though locatednear the middle of the forbidden gap, the topological states are rather extended in one directionwhile being centered at under- and overcoordinated atoms. The states exhibit the reverse charge-spinrelation, the majority of states being diamagnetic and charged. The topological states may besufficient to account for a number of irradiation-induced phenomena in amorphous semiconductors,including electron spin resonance signal, midgap absorption, photoluminescence, and the fatigue ofphotoluminescence. We propose experiments to test the present microscopic picture.