Trapping and recombination in amorphous hydrogenated silicon studied by dual-beam-modulated photoconductivity

Abstract

The frequency-dependent spectrum of dual-beam-modulated photoconductivity reveals that various processes contribute to steady-state photoconductivity in undoped a-Si: H. These are

1.	electron thermal emission from doubly-occupied dangling bonds
2.	electron thermal emission from localized states of the conduction-band tail, and
3.	quenching of photoconductivity which proceeds by reducing the density of electrons trapped on dangling bonds.

These results are obtained on the basis of a model which in particular allows the coefficient γ characterizing the generation rate dependence of photoconductivity (σ_pαf^y _p) to be related to the coefficients γ_i(i = 1—3) characterizing processes 1—3: γ = a ₁γ₁ + a ₂γ₂ — a ₃γ₃, where a _i is a dimensionless parameter describing the relative contribution of process i. The temperature and the photogeneration rate dependences of these processes studied in the annealed and in the light-soaked states are used to identify the nature of the quenching process.