Structure in amorphous semiconductors: Extrinsic and intrinsic

The amorphous compound semiconductors contain chemical disorder in addition to structural disorder. As formed, amorphous compound semiconductors including the Ga and In phosphides and arsenides all exhibit chemical disorder manifested as homopolar bonding. Though low-temperature thermal annealing lessens the Debye-Waller factor and the homopolar bonding fraction, the latter is not eliminated. Point-defect annealing in the form of homopolar bond annihilation is thus operative during structural relaxation of the amorphous phase. Residual chemical disorder necessitates the presence of odd-membered rings and thus demonstrates the elastic energy required to produce a continuous-random-network without homopolar bonding (or equivalently with only even-membered rings) must exceed the Coulomb energy inherent with anion-anion or cation-cation repulsion.