Intrinsic coherent acoustic phonons in the indirect band gap semiconductors Si and GaP
Intrinsic coherent acoustic phonons in the indirect band gap semiconductors Si and GaP
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DOI：
10.1103/physrevb.95.035205
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发表时间：
2017-01-18
影响因子：
3.7
通讯作者：
Stanton, Christopher J.
中科院分区：
文献类型：
--
作者：
Ishioka, Kunie;Rustagi, Avinash;Stanton, Christopher J.
我们报告了（001）取向块体 Si 和 GaP 上相干声声子的本征光学生成和检测，无需金属声子换能器结构。 3.1 eV 激光脉冲的光激发在两种半导体中产生类似于 100 nm 穿透深度的法向应变脉冲。使用延迟光学探针检测应变脉冲随后传播到体中的情况，作为光学反射率的周期性调制。我们的理论模型定量地解释了通过变形势电子声子耦合和检测两种半导体的空间和时间相关光弹性效应来产生声脉冲。与我们的理论模型的比较表明，GaP 和 Si 的实验应变脉冲具有 1.2 和 0.4 ps 的有限建立时间，这与光激发电子通过层间散射转移到最低 X 谷所需的时间相当。根据我们的实验，与声脉冲生成相关的 GaP 的变形势耦合估计是 Si 的两倍，这与之前的理论预测一致。
We report on the intrinsic optical generation and detection of coherent acoustic phonons at (001)-oriented bulk Si and GaP without metallic phonon transducer structures. Photoexcitation by a 3.1-eV laser pulse generates a normal strain pulse within the similar to 100-nm penetration depth in both semiconductors. The subsequent propagation of the strain pulse into the bulk is detected with a delayed optical probe as a periodic modulation of the optical reflectivity. Our theoretical model explains quantitatively the generation of the acoustic pulse via the deformation potential electron-phonon coupling and detection in terms of the spatially and temporally dependent photoelastic effect for both semiconductors. Comparison with our theoretical model reveals that the experimental strain pulses have finite buildup times of 1.2 and 0.4 ps for GaP and Si, which are comparable with the time required for the photoexcited electrons to transfer to the lowest X valley through intervalley scattering. The deformation potential coupling related to the acoustic pulse generation for GaP is estimated to be twice as strong as that for Si from our experiments, in agreement with a previous theoretical prediction.