利用MOCVD在r面蓝宝石上生长的α面GaN中两步AlN缓冲层的优化

摘要

采用两步AlN缓冲层(一层低温AlN和一层高温AlN)在r面蓝宝石衬底上生长了非极性的α面GaN,并利用高分辨X射线衍射和光致荧光谱对所生长的材料进行了研究.两步AIN缓冲层在我们之前的工作中已被证明比单步高温AlN或低温GaN缓冲层更有利于减小材料各向异性和提高晶体质量,本文进一步优化了两步AlN缓冲层的结构,并得到了各向异性更小,晶体质量更好的α面GaN薄膜.分析表明,两步AlN缓冲层中的低温AlN层在减小各向异性中起着关键作用.低温AlN层能抑制了优势方向(c轴)的原子迁移,有利于劣势方向(m轴)的原子迁移,从而减小了Al原子在不同方向迁移能力的差异,并为其后的高温AlN缓冲层和GaN层提供"生长模板",以得到各向异性更小、晶体质量更好的α面GaN材料.%Nonpolar (1120) a-plane GaN films with two-step AIN buffer(a low-temperature (LT) and a high-temperature (HT) A1N layers) were grown on (1102) r-plane sapphire by metalorganic chemical vapor deposition (MOCVD). The as-grown films were investigated by high-resolutian X-ray diffraction ( XRD ) and photoluminescence (PL). The two-step AIN buffer has been proved to be advantageous in crystal quality compared with one-step LT-GaN or HT-AIN buffers in our early works. In this report, the thickness of the two-step buffer was further optimized, and much less anisotropic a-plane (GaN films were achieved. It was found that the LT-AIN layer of the two-step buffer played a key role in reduction of anisotropy of the GaN film grown.