Yoshikawa Masanobu, Seki Hirohumi, Inoue Keiko, Kobayashi Takuma, Kimoto Tsunenobu
Appl Spectrosc. 2015 Sep 1. doi: 10.1366/14-07833.
We measured the Fourier transform infrared (FT-IR) spectra of thermal oxides with various thicknesses, grown thermally on 4H silicon carbide (4H-SiC) substrates. For the thin (8 nm thick) thermal oxide, the transverse optical (TO) phonon peak frequency in the thermal oxide on the 4H-SiC substrate was observed at ~1080 cm and was higher than that recorded in thermal oxides on a Si substrate (1074 cm). This shows that the thin thermal oxide was under compressive stress, calculated to be approximately 0.4 GPa, at the interface between the thermal oxide and 4H-SiC substrate. The shift of the TO phonon for s-polarized light was found to be larger than that for p-polarized light. In contrast, for the thick (85 and 130 nm thick) thermal oxides, the TO phonon peak frequency tended to shift toward lower frequencies with increasing oxide-layer thickness. By comparing the FT-IR and cathodoluminescence (CL) measurements, we conclude that the TO phonon redshift with increasing oxide-layer thickness can mainly be attributed to a corresponding increase in inhomogeneity in the thick thermal oxides.
我们测量了在4H碳化硅（4H-SiC）衬底上热生长的不同厚度热氧化物的傅里叶变换红外（FT-IR）光谱。对于薄（8纳米厚）的热氧化物，在4H-SiC衬底上的热氧化物中，横向光学（TO）声子峰频率在~1080厘米处被观测到，并且高于在硅衬底上的热氧化物中记录的频率（1074厘米）。这表明在热氧化物与4H-SiC衬底的界面处，薄热氧化物处于约0.4吉帕的压应力下。发现s偏振光的TO声子位移大于p偏振光的位移。相比之下，对于厚（85和130纳米厚）的热氧化物，TO声子峰频率倾向于随着氧化层厚度的增加而向更低频率移动。通过比较FT-IR和阴极发光（CL）测量结果，我们得出结论，TO声子随氧化层厚度增加的红移主要可归因于厚热氧化物中不均匀性的相应增加。
