16 June 2004 Coherent phonon spectroscopy of semiconductor-metal interfaces
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Coherent phonons of semiconductor-metal interfaces are impulsively generated and detected with time-resolved second-harmonic generation. Coherent longitudinal optical phonons are launched in the near surface depletion regions of GaP/Au and GaAsP/Au Schottky photodiodes. Photoexcited electrons ballistically transport from the metal layer into the semiconductor region rapidly screen the near surface depletion field and launches these coherent LO phonons. The dephasing of these coherent LO phonons is mainly due to the anharmonic decay at zero or reverse bias. Their dephasing times decrease significantly as a forward bias is applied to the heterointerface. This effect is attributed to the strong carrier-phonon scatterings induced by the electrical driven electrons flowing across the heterointerface. Meanwhile, coherent longitudinal acoustic wave packet is observed in the GaP/Au heterointerface via transient thermal absorption in the gold thin layer. This acoustic wave packet propagates into the GaP bulk with the sound velocity ~5.8×105 cm/sec of GaP LA phonon.
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Yu-Ming Chang, Yu-Ming Chang, } "Coherent phonon spectroscopy of semiconductor-metal interfaces", Proc. SPIE 5352, Ultrafast Phenomena in Semiconductors and Nanostructure Materials VIII, (16 June 2004); doi: 10.1117/12.528718; https://doi.org/10.1117/12.528718

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