Chisato Ogihara

Nature of trapped hole centres (A centres) in a-Si:H : Investigation by optically detected magnetic resonance and photoinduced absorption measurements on a-Si:Ha-Si1−xNx:H superlattices

Abstract Nature of the trapped hole centres (A centres) has been elucidated by optically detected magnetic resonance and photoinduced absorption measurements on a-Si:H a-Si 1−x N x :H superlattices. The results are discussed in terms of a model of self-trapped holes for the A centres.

Gap states and recombination processes in one-dimensionally ordered and disordered a-Si : H/a-Si1−xNx:H multilayer films

Abstract Properties of a-Si:H/a-Si1−xNx:H multilayer films with and without disorder of the well-layer thickness have been investigated by measurements of ODMR, PL, PA and PA-detected ESR. The results are discussed in terms of a quantum-well model and interface states.

Electron-Hole Recombination in a-Si:H/ a-Si1-xNx:H Superlattices as Elucidated by Time-Resolved Luminescence and Optically Detected Magnetic Resonance Measurements

Time-resolved luminescence and time-resolved ODMR measurements have been carried out on a-Si:H / a-Si 1- x N x :H superlattices and electron-hole recombination processes in these superlattices have been studied. Nonradiative recombination is suppressed in the superlattices by its two-dimensional feature when the well-layer thickness, L w , is much smaller than the average spatial separation of dangling bonds. Radiative recombination is enhanced by an increase in density of electrons and holes due to the confinement effect. But the radiative recombination rate is reduced by its two-dimensional feature when the well-layer thickness is very small ( L w <10 A). The time-resolved luminescence spectra shift towards higher energy and are broadened with decreasing L w . These results are explained in terms of a quantum-well model.

Time-Resolved Optically Detected Magnetic Resonance Experiment on Conduction Band Tail Electrons and A Centres in Hydrogenated Amorphous Silicon

The conduction band tail electron resonance was observed at 2 K in a-Si:H by time-resolved optically detected magnetic resonance experiments, using intense pulsed excitation. The exchange interaction between the tail electrons and the trapped holes at A centres was elucidated by the observation of shift of the A centre g -value with delay time of the microwave pulse after pulsed excitation. Dynamical processes of radiative and nonradiative recombination are discussed on the basis of the experimental results,

Time-resolved optically detected magnetic resonance in a-Si:H/a-Si1−xNx:H superlattices

Abstract Time-resolved (TR) ODMR and TR-luminescence measurements have been carried out at 2 K for a-Si:H/a-Si 1−x N x :H superlattices. Experimental results are interpreted in terms of a quantum-well model and interface states.

Preparation and optical absorption spectra of a new type of artificial semiconducting material: Band-edge-modulated a-Si1-xNx:H films

Abstract We have prepared band-edge-modulated a-Si1-xNx:H films in which the edges of the conduction and valence bands are modulated with an approximately sinusoidal function. The optical gap of the films is linearly dependent on the inverse of the modulation period. This result is interpreted in terms of the quantized levels derived using effective-mass equations for electrons and holes in their respective bands under the influence of the modulating potentials.

Optical properties of band-edge modulated a-Si1−xNx:H films

Abstract The optical absorption spectra and photoluminescence spectra have been measured for a new type of artificial semiconducting materials, called the band-edge modulated a-Si1−xNx:H films, in which the edges of conduction band and valence band are almost modulated with a sinusoidal function. The quantum size effect on both spectra has been observed and is interpreted in terms of the quantized levels along a direction perpendicular to deposited layers.

Optical Absorption Spectra of Band-Edge Modulated a-Si1-xNx:H Films

We have prepared a-Si1-xNx:H samples which have a sinusoidally modulated band-edge structure. The period, L, ranges between 30 A and 300 A. The optical absorption spectra have been measured and the optical gap has been obtained for the samples, The optical gap increases with decreasing L. This result can be explained in terms of an effective mass equation for electrons and holes in respective bands under the modulated potentials.

Conduction band tail electrons and a centres in a-Si:H as elucidated by time-resolved optically detected magnetic resonance measurements

Abstract We have observed the tail electron resonance in a-Si:H by time-resolved optically detected magnetic resonance experiments, using intense pulsed excitation. The exchange interaction between the tail electrons and the trapped holes at the A centres was revealed by the observation of shift of the A centre g-value with delay time of the microwave pulse after pulsed excitation.

Characterization of a-Si:H/a-Si1−xNx:H superlattice films by photoluminescence measurements: The correlation between the preparation condition and the film quality

Abstract Using the r.f. glow dischargeteechnique, a-Si: H/a-Si 1−x N x :H superlattices were fabricated by varying the preparation conditions such as the substrate temperature, the interrupting interval of the r.f. plasma, the gas-flow condition and the kinds of gases for the barrier layer. The correlation between these parameters and the film quality is evaluated by the photoluminescence measurements.