Majority and minority carrier lifetimes in doped a-Si junctions and the energy of the dangling-bond state

Electron and hole lifetimes have been measured by transient-delayed-field techniques on a series of a-Si junction specimens deposited with lightly doped n- or p-type central regions. The results, plotted as a function of Fermi level position, show a pronounced sensitization of the majority carriers and a desensitization of the minority carriers. The data are readily explained by electron and hole capture at the dangling-bond centre. An analysis of this centre in terms of the occupation statistics places it at an energy between 0·95 and 1·0 eV below εc. The assignment is supported by independent results, but disagrees with recent spectroscopic work.