Optimization of High-Quality AlN Epitaxially Grown on (0001) Sapphire by Metal-Organic Vapor-Phase Epitaxy
Optimization of High-Quality AlN Epitaxially Grown on (0001) Sapphire by Metal-Organic Vapor-Phase Epitaxy
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DOI：
10.1007/s11664-007-0099-3
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发表时间：
2007-05
影响因子：
2.1
通讯作者：
Y. Xi;K. Chen;F. Mont;J. K. Kim;E. Schubert;C. Wetzel;W. Liu;X. Li;J. Smart
中科院分区：
文献类型：
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作者：
Y. Xi;K. Chen;F. Mont;J. K. Kim;E. Schubert;C. Wetzel;W. Liu;X. Li;J. Smart
系统地研究了用金属-有机气相外延技术在(0001)蓝宝石衬底上生长氮化铝(AlN)外延层。具体而言，研究了氮化铝成核条件对氮化铝外延层结晶质量和表面形貌的影响。原子力显微镜(AFM)和X射线衍射仪(XRD)结果表明，成核层对后续层的生长起着关键作用。AlN成核层的TMAl流的大小对高温AlN外延层的结晶质量和表面形貌有很大的影响。提出了一个简单的Al吸附原子扩散增强模型来解释TMAl流动对晶体质量和表面形貌的强烈依赖。此外，氨气流量、成核温度和AlN成核层的生长时间对AlN的表面形貌和结晶质量也有影响。表面形态和晶体质量之间存在权衡，即对于相同的生长参数，我们不能获得最好的表面形态和最高的晶体质量。对于优化的AlN成核层和高温AlN外延层，AFM在AlN外延层上发现了清晰且连续的锯齿状阶梯状线形流动模式。三轴X射线摇摆曲线显示(002)和(004)反射的半高全宽(FWHM)分别为11.5和14.5弧秒。根据原子力显微镜的测量，KOH腐蚀显示出2×107 cm−2的蚀坑密度(EPD)。
A systematic study is performed to optimize aluminum nitride (AlN) epilayers grown on (0001) sapphire by metal-organic vapor-phase epitaxy. Specifically, the impact of the AlN nucleation conditions on the crystalline quality and surface morphology of AlN epilayers is studied. Atomic force microscopy (AFM) and x-ray diffraction (XRD) results reveal that the nucleation layer plays a critical role in the growth of subsequent layers. The magnitude of the TMAl flow of AlN nucleation layer is found to have a strong effect on the crystalline quality and surface morphology of the high-temperature (HT) AlN epilayer. A simple Al adatom-diffusion-enhancement model is presented to explain the strong dependence of the crystalline quality and surface morphology on TMAl flow. Furthermore, ammonia flow, nucleation temperature, and growth time of the AlN nucleation layer are found to affect the surface morphology and the crystalline quality as well. A trade-off is found between surface morphology and crystalline quality; that is, we do not obtain the best surface morphology and the highest crystalline quality for the same growth parameters. For optimized AlN nucleation layers and HT AlN epilayers, a clear and continuously linear step-flow pattern with saw-tooth shaped terrace edges is found by AFM on AlN epilayers. Triple-axis x-ray rocking curves show a full-width at half-maximum (FWHM) of 11.5 arcsec and 14.5 arcsec for the (002) and (004) reflection, respectively. KOH etching reveals an etch-pit density (EPD) of 2 × 107cm−2, as deduced from AFM measurements.