Researchers Sergio Revuelta, Hai I. Wang, Mischa Bonn, and Enrique Canovas from the Netherlands’ FOM Institute AMOLF have made a significant observation related to the thermal behavior of photoexcited shallow defects in high-resistivity silicon. Their work, published in the journal Nature Communications, sheds light on the dynamics of charge carriers in silicon, which has practical implications for the energy industry, particularly in the development of more efficient optoelectronic devices.
The team employed time-resolved terahertz (THz) spectroscopy to study the behavior of silicon when exposed to near-band-gap light. They observed a pronounced temporal delay in photoconductivity, indicating that a fraction of the photogenerated charge carriers was temporarily trapped immediately after excitation. This delay was attributed to the presence of a localized shallow state situated approximately 40 meV from the band edge, which competes with silicon’s indirect band-to-band absorption.
The researchers analyzed the frequency-resolved complex photoconductivity as a function of pump-probe delay and photon energy. They found that the zero-order kinetic profile of the temporal delay, its invariance with respect to photon flux, and its temperature dependence collectively support the existence of a phonon bottleneck. This bottleneck hinders the thermal release of electrons from the shallow trap, representing experimental evidence of a phonon bottleneck effect associated with the thermal activation of shallow traps in photoexcited silicon.
The practical applications of this research for the energy sector are significant. Understanding the carrier relaxation dynamics in silicon and the role of electron-phonon interactions in ultrafast processes can lead to the development of more efficient optoelectronic devices. These devices are crucial for various energy applications, including solar cells, photodetectors, and optical communication systems. By optimizing the design and performance of these devices, the energy industry can benefit from improved energy conversion efficiencies and enhanced operational capabilities.
In summary, the research conducted by Revuelta and his colleagues provides valuable insights into the behavior of photoexcited shallow defects in silicon. Their findings highlight the importance of phonon bottleneck effects and electron-phonon interactions, paving the way for advancements in optoelectronic technologies that are vital for the energy industry.
Source: Nature Communications, “Observation of a phonon bottleneck effect on the thermal depopulation from a photoexcited shallow defect in silicon”
This article is based on research available at arXiv.