光子动量介导带间跃迁的飞秒激光诱导硅金属化

中文摘要 AI 辅助

硅基技术自电子革命开启以来始终处于电子与光子研究的前沿。然而，硅本质上是间接带隙半导体：导带最小值与价带最大值位于动量空间的不同点，因此光跃迁需要声子辅助以守恒晶体动量。这种三体电子-光子-声子相互作用使硅在太阳能电池、光电器件等光吸收应用中效率低下。本研究在已确立的纳米级光子动量限域机制（该机制拓宽光子动量分布，使硅实现无 phonon 吸收）基础上，随后施加高强度飞秒脉冲激发，注入超过莫特密度的热载流子，使带隙坍缩并诱导可逆的半导体-金属转变。纳米级光子动量限域此前已被证实，本研究核心贡献在于这一后续的载流子密度驱动阶段，该阶段将动量增强区域驱动至可逆瞬态金属相。模拟结果显示，材料呈现高负介电常数、增强的光功率吸收、大吸收系数及低趋肤深度，载流子密度达到远超莫特阈值的显著值；研究证实，在低于硅熔化阈值的条件下可实现载流子驱动的金属化且操作稳定。这些结果确立了在硅中动态诱导金属态的通用机制，为在传统 CMOS 平台内实现单片集成的有源光子组件及动态可重构电光器件提供了潜在途径。

英文摘要

Silicon-based technology has been at the forefront of electronic and photonic research since the dawn of the electronic revolution. However, silicon is fundamentally an indirect-bandgap semiconductor: the conduction band minimum and valence band maximum occur at different points in momentum space, so optical transitions require phonon assistance to conserve crystal momentum. This three-body electron-photon-phonon interaction renders silicon an inefficient material for light-absorbing applications such as solar cells and optoelectronic devices. In this work, we build on an established nanoscale photon-momentum confinement mechanism, which broadens the photon momentum distribution and enables phonon-free absorption in silicon, by subsequently applying a high-intensity femtosecond pulsed excitation that injects hot carriers beyond the Mott density, collapsing the bandgap and inducing a reversible semiconductor-to-metal transition. While nanoscale photon-momentum confinement itself has been previously established, the central contribution of this work is this subsequent, carrier density-driven stage, which drives the momentum-enhanced region into a reversible transient metallic phase. Our simulations report highly negative permittivity, enhanced optical power absorption, a large absorption coefficient, and low skin depth, with carrier densities reaching a notable value, far exceeding the Mott threshold. We have shown carrier driven metallization with stable operation below melting threshold of silicon. These results establish a general mechanism for dynamically inducing metallic states in silicon, offering a potential pathway toward monolithically integrated active photonic components and dynamically reconfigurable electro-optical devices within conventional CMOS platforms.

发表机构

• North South University（北南大学）

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