Photo-excited charge carriers suppress sub-terahertz phonon mode in silicon at room temperature

• Published in: Nature communications 2016-10, Vol.7 (1), p.13174-13174, Article 13174
• Main Authors: Liao, Bolin, Maznev, A. A., Nelson, Keith A., Chen, Gang
• Format: Article
• Language: English
• Subjects: 140/125; 639/301/299/2736; 639/4077/4107; 639/766/119/1000; Electrons; Humanities and Social Sciences; multidisciplinary; Neutrons; Science; Science (multidisciplinary); Semiconductors; Silicon; solar (photovoltaic), solar (thermal), solid state lighting, phonons, thermal conductivity, thermoelectric, defects, mechanical behavior, charge transport, spin dynamics, materials and chemistry by design, optics, synthesis (novel materials), synthesis (self-assembly), synthesis (scalable processing); Temperature
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/ncomms13174

There is a growing interest in the mode-by-mode understanding of electron and phonon transport for improving energy conversion technologies, such as thermoelectrics and photovoltaics. Whereas remarkable progress has been made in probing phonon–phonon interactions, it has been a challenge to directly measure electron–phonon interactions at the single-mode level, especially their effect on phonon transport above cryogenic temperatures. Here we use three-pulse photoacoustic spectroscopy to investigate the damping of a single sub-terahertz coherent phonon mode by free charge carriers in silicon at room temperature. Building on conventional pump–probe photoacoustic spectroscopy, we introduce an additional laser pulse to optically generate charge carriers, and carefully design temporal sequence of the three pulses to unambiguously quantify the scattering rate of a single-phonon mode due to the electron–phonon interaction. Our results confirm predictions from first-principles simulations and indicate the importance of the often-neglected effect of electron–phonon interaction on phonon transport in doped semiconductors. Direct measurement of electron-phonon interactions at the single-mode level has been a challenge. Here, Liao et al . use a three-pulse photoacoustic spectroscopy technique to investigate the damping of a single sub-terahertz coherent phonon mode by photo-excited free charge carriers in silicon at room temperature.