Abstract
Photoluminescence decay has been studied for five a-Si: H/a-Si3N4: H multilayer structures with different well-layer thicknesses of 8, 13, 25, 50 and 400 Å and a common barrier-layer thickness of 100 Å. The decay curves are compared with that observed for an a-Si: H film with a thickness of 1 pm. At liquid-helium temperature the photoluminescence has a long effective decay time of 2·5 × 10−3s and this is interpreted in terms of recombination of localized excitons. Above liquid-nitrogen temperature the photoluminescence can be described by a double hyperbolic decay function and interpreted as exciton recombination combined with dispersive diffusion originating from a fractal-time random walk and a random walk on a fractal network.