Raman scattering from LO phonon-plasmon coupled modes and Hall-effect in n-type silicon carbide 4H-SiC
Raman scattering from LO phonon-plasmon coupled modes and Hall-effect in n-type silicon carbide 4H-SiC
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DOI：
10.1063/1.1410884
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发表时间：
2001-11-15
影响因子：
3.2
通讯作者：
Mitchel, WC
中科院分区：
文献类型：
--
作者：
Chafai, M;Jaouhari, A;Mitchel, WC
SiC的输运特性，特别是自由载流子密度和迁移率，通常由霍尔效应决定。拉曼光谱已被证明产生类似于霍尔效应的输运参数。掺杂SiC中的纵向光学等离子体激元耦合（LOPC）模式的分析提供了这样的信息。在n型4 H-SiC中的阻尼等离子体激元的情况下，载流子浓度的变化导致LOPC模式的频移，其看起来接近A（1）（LO）声子模式。不同的自由载流子浓度（等离子体频率）和迁移率（等离子体阻尼常数）的这种方法的有效性进行了分析。理论计算结果表明，在低载流子浓度下，由LOPC模的频移可以可靠地估计自由载流子密度。在这样的载流子浓度下，建立了LOPC模式的拉曼位移与等离子体频率之间的可靠相关性，而没有等离子体激元阻尼常数的显著影响。然而，当自由电子浓度增加时，观察到等离子体激元阻尼常数对LPOC模式的拉曼频移的不可忽略的影响。因此，可靠的传输数据只能通过完整的线形分析来获得。这些结果得到了自由电子浓度在1 × 10 ~（17）~ 5 × 10 ~（18）cm ~（-3）之间的n型4 H-SiC块体样品的实验结果的证实。(C)2001年美国物理学会。
The transport properties, particularly free carrier density and mobility, of SiC are usually determined by the Hall effect. Raman spectroscopy has been shown to yield transport parameters similar to the Hall effect. The analysis of the longitudinal optical plasmon coupled (LOPC) modes in doped SiC provides such information. In the case of damped plasmons in n-type 4H-SiC, changes in the carrier concentration result in a frequency shift of the LOPC mode, which appears close to the A(1)(LO) phonon mode. The validity of this approach for different free carrier concentrations (plasma frequencies) and mobilities (plasmon damping constants) is analyzed. The theoretical results obtained show that reliable estimation of the free carrier density can be obtained from the frequency shift of the LOPC mode for low carrier concentrations. At such a carrier concentration a reliable correlation between the Raman shift of the LOPC mode and the plasma frequency is established, without noticeable influence of the plasmon damping constant. However, when the free electron concentration increases, a non-negligible influence of the plasmon damping constant on the Raman frequency shift of the LPOC mode is observed. Therefore reliable transport data can only be obtained by a full line-shape analysis. These results are confirmed by the experimental results obtained on n-type 4H-SiC bulk samples with free electron concentration between 1x10(17) and 5x10(18) cm(-3). (C) 2001 American Institute of Physics.