摘要
The results of second-order Raman-scattering experiments on n- and p-type 4H-SiC are presented,covering the acoustic and the optical overtone spectral regions.Some of the observed structures in the spectra are assigned to particular phonon branches and the points in the Brillouin zone from which the scattering originates.There exists a doublet at 626/636cm -1 with energy difference about 10cm -1 in both n- and p-type 4H-SiC,which is similar to the doublet structure with the same energy difference founded in hexagonal GaN,ZnO, and AlN.The cutoff frequency at 1926cm -1 of the second-order Raman is not the overtone of the A 1(LO) peak of the n-type doping 4H-SiC,but that of the undoping one.The second-order Raman spectrum of 4H-SiC can hardly be affected by doping species or doping density.
给出了 n型和 p型 4 H- Si C的二级喇曼谱的实验结果 .指认了所观察到的一些光谱结构对应的特定声子支及其在布里渊区中相应的对称点 .发现在 4 H- Si C的二级喇曼谱中存在能量差约为 10 cm- 1的双谱线结构 ,这一结构与六方相 Ga N,Zn O和 Al N的双谱线结构具有相同的能量差 .二级喇曼谱的截止频率对于不同掺杂情况的 4 H- Si C具有相同的值 .它并不等于 n型掺杂 4 H- Si C的 A1 (L O)声子的倍频 ,而是等于未掺杂样品的 A1 (L O)声子的倍频 .掺杂类型和杂质浓度对 4 H- Si C的二级喇曼谱几乎没有影响 .
