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采用镀Ti插入层在氢化物外延设备中制备了高质量自支撑GaN厚膜。X射线衍射测试发现(0002)峰摇摆曲线的半高宽为260arcsec;5K下样品带边发光峰的半高宽为3meV,室温下样品的带边发光峰也只有20meV,并且在室温的PL谱中观察不到黄光带;扫描电子显微镜观察显示,腐蚀后的自支撑GaN厚膜表面有位错延伸形成的六角坑,并估算出样品位错密度约为2.1×l07cm-2。这些结果说明镀Ti插入层有助于提高GaN外延层的晶体质量。通过Raman和低温荧光分析,可以看出自支撑GaN厚膜表面应力已经完全释放。研究了不同温度下样品的荧光特性,证明得到的无应力自支撑GaN厚膜具有很好的晶体质量和光学质量。
A high quality self-supporting GaN thick film was prepared in a hydride epitaxial apparatus using a Ti-plated interposer. The full width at half maximum (FWHM) of the (0002) peak rocking curve was 260 arcsec by X-ray diffraction. The full width at half maximum of the band edge emission peak at 5K was 3 meV, and the band edge emission peak was only 20 meV at room temperature. No yellow band was observed. Scanning electron microscopy showed that hexagonal pits were formed on the surface of the etched self-supporting GaN thick film with dislocation extension, and the estimated dislocation density was about 2.1 × 10 7 cm -2. These results show that the Ti-plated interlayers contribute to improving the crystal quality of the GaN epitaxial layer. By Raman and low temperature fluorescence analysis, it can be seen that the surface stress of free-standing GaN thick film has been completely released. The fluorescence characteristics of samples at different temperatures were investigated. The results show that the obtained stress-free self-supporting GaN thick film has good crystal quality and optical quality.