Luminescence and absorption edge of a-Ge:H well layers in a-Si:H/a-Ge:H multilayers

The fundamental absorption edge spectra of a-Ge:H well layers with thickness of 1.0, 1.5, 2.5 and 4.0 nm in the a-Si:H/a-Ge:H multilayers have been obtained in the absorption coefficient range from 10 to 106 cm−1 by combining the luminescence excitation spectra with the optical transmission spectra at 15 K. The fundamental absorption edge spectra of the well layers have Urbach tails with slopes of about 50 meV. The luminescence decays of the a-Ge:H well layers have been measured in the time range from 10−7 to 10−2 s. The luminescence decays of the well layers at 15 K are described by a power law decay, t−δ, with δ∼1.2.