Subgap Density Of States Research Articles

Amorphous Silicon-Carbon Alloys and Amorphous Carbon from Direct Methane and Ethylene Activation by ECR

ABSTRACTHydrogenated amorphous silicon-carbon alloys are prepared using electron-cyclotron resonance (ECR) plasma-enhanced chemical vapor deposition. Hydrogen is introduced into the source resonance cavity as an excitation gas. Silane is introduced in the main chamber in the vicinity of the plasma stream, whereas the carbon source gases, methane or ethylene, are introduced either with the silane or with the hydrogen as excitation gases. The effect of the type of carbon-source gas, excitation gas mixture and silane-to-carbon source gas flow ratio on the deposition rate, bandgap, subgap density of states, spin density and hydrogen evolution are studied.

Light intensity dependence of the photoconductivity of hydrogenated amorphous silicon

Abstract The physical meaning of the exponent γ characterizing the light intensity dependence of the photoconductiyity σ p in hydrogenated amorphous silicon is investigated on the basis of a dual-beam modulated photoconductiyity (DBMP) analysis. The frequency-dependent spectrum can be resolyed into three components which at high temperatures are due to thermal re-emission of electrons from D− centres, thermal re-emission of electrons from tail states and electron-hole recombination. It is found that each component follows its own generation rate dependence with an exponent γ i ≠ γ. On this basis a model is established which allows firstly σ p to be related to the components separated by DBMP, secondly each component to be characterized by its relative weight a i such that Σa i γ i,= 1, thirdly the dependence of γ on the position of the quasi-Fermi level in the gap to be related to the variations in Σa i and fourthly the weights a i and the subgap density of states to be quantitatively correlated. Experime...