Electronic properties of noncrystalline semiconductors

Abstract

The electronic properties of inorganic noncrystalline semiconductors are reviewed in this chapter using the effective mass approach in the real coordinate space. It is shown that many properties that can be studied through the effective mass approximation applied in the reciprocal lattice vector k-space in crystalline semiconductors can be studied in noncrystalline semiconductors in the real coordinate r-space. The effective masses of electrons and holes are derived in their respective extended and tail states within the real coordinate space. The mechanism of the double sign reversal leading to the anomalous Hall effect observed in hydrogenated amorphous silicon (a-Si: H) has been successfully explained using the theory of effective mass. It is demonstrated that excitons can also be formed in noncrystalline semiconductors and the energy difference between the singlet and triplet exciton energies is larger than in crystalline semiconductors. The application of the new time-dependent exciton-spin-orbit-photon interaction derived recently by the author has been reviewed for harvesting the radiative emission from triplet excitons, where the traditional perturbation approach cannot be applied very successfully.