Abstract
The anti-Stokes Raman scattering of a-Si and a-Si:H is studied at T=2 K for intense (∼1 mJ/mm 2 ) pulsed optical excitation. It is found that high-energy phonons (hω>100 cm -2 ) emitted as a result of carrier relaxation possess a nonequilibrium energy distribution. A time-resolved study of the Raman signals reveals relaxation time constants for 480-cm -1 phonons as long as 1B ns. The effect of phonon localization is suggested as an explanation of the experimental results
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