Recombination processes ina-Si: H. A study by optically detected magnetic resonance

We report cw and time-resolved optically detected magnetic resonance data on samples of $a$-Si: H prepared by reactive sputtering, glow-discharge, and chemical vapor deposition. Two distinct luminescence processes are inferred near 1.3-1.4 and 0.9 eV. An enhancing signal at $g=2.0065\mathrm{}$ is observed on the 0.9-eV photoluminescence (PL) band and is linked to distant-pair radiative recombination between a dangling bond and a hole localized in a valence-band tail state. The high-energy PL band shows a quenching resonance at $g=2.005\mathrm{}$, which can be associated with shunt processes involving dangling bonds. Enhancing signals are also observed on this high-energy band: In lowdefect-density sputtered samples, a 200-G-wide line at $g\simeq 2.01$ is associated with short radiative lifetimes (∼ms) and narrows for longer lifetimes (∼s). In all other samples studied, a narrower line (19 G) at $g=2.0078\mathrm{}$ is linked to short lifetimes and broadens for longer lifetimes. Both signals are consistent with a model in which the high-energy PL band arises from radiative recombination of carriers localized in band tail states, and are successfully explained by exchange interaction.