利用拉曼散射光谱对在SiC衬底上采用MOCVD异质外延的未故意掺杂GaN薄膜特性进行研究发现E2模式向频率低的方向漂移表明在GaN薄膜中存在张力,由于SiC衬底不平整度增加引起更多位错的出现,从而引起拉曼谱中E2模式的加宽,因此通过选择平整度较好的衬底可以减小缺陷密度,提高薄膜的质量,此外A1(LO)模式的出现与强度可以用来表征未掺杂GaN的薄膜质量.

The properties of undopedGaN layers grown by MOCVD on SiC substrate were studied using Raman scattering spectra, The result indicate that there is tensile stress in GaN films since the E₂ mode shifted to low frequency, with the roughness of SiC substrate being worse, much more dislocation is introduced and FWHM of E₂ mode increased. Therefore the smooth substrate should be selected to decrease the defect density and improve the quality of the GaN , furthmore, whether A₁(LO) mode existing or not and the intensity of A₁(LO) can be used to identify the quality of GaN film.