Vibrational characteristics of acceptor-hydrogen complexes in silicon

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Abstract
Acceptor-hydrogen complexes for the group III acceptors, B, Al, and Ga, in Si have been studied with low-temperature infrared spectroscopy. The Si-H stretching band narrows dramatically upon cooling to low temperature thereby aiding the detection of the vibrations of the Al and Ga acceptor-H complexes. The frequency 2201 cm−1 we have measured for the Al-H complex is in reasonable agreement with the prediction made by G. G. DeLeo and W. B. Fowler [Phys. Rev. B 31, 6861 (1985)] (2220 cm−1 for a 〈111〉 interstitial configuration for the H). Assignment of the new vibrational bands is confirmed by isotopic substitution. The strength of the absorption provides evidence that the passivation is not the result of compensation alone and that a major fraction of the passivated acceptors result in acceptor-H complexes. A new, low-energy excitation of the acceptor-hydrogen complexes gives rise to a sideband to the main stretching vibration and explains the pronounced energy shift and narrowing of the spectra upon cooling to He temperature.