Hydrogen-induced defects in ion-implanted Si

Single crystalline silicon implanted with Si-28 ions and subsequently hydrogenated from an rf plasma at 200 degrees C is studied by Raman and photoluminescence spectroscopy. A broad Raman band at 3830 cm(-1) previously assigned to the rovibrational transitions of hydrogen molecules trapped in Si multivacancies [Ishioka et al., Phys. Rev. B 60, 10852 (1999)] reveals a complex line shape at 60 K. In contrast, our study correlates the Raman band to three different localized traps for hydrogen molecules which are identified from the dependence on the ion dose and annealing behavior. Each of these traps, which is saturated with H-2, gives rise to three Raman transitions due to para-and ortho-H-2. The H-2 signals are shown to correlate with the Si-H vibrational modes at 1888, 1930, and 1964 cm(-1). Ortho to para conversion rates of H-2 at 77 K and room temperature were found to be 62 +/- 15 and 8 +/- 2 h, respectively.