应用厚缓冲层实现蓝宝石上高质量AlN外延层的MOCVD生长

MOCVD Growth of High Quality AlN on Sapphire Substrate by Introducing Thick Buffer Layer

在蓝宝石衬底上采用由低温AlN成核层、中温AlN生长层、温度渐变AlN生长层和高温AlN生长层组成的厚三维生长缓冲层来实现AlN外延层位错密度的减少和应力的释放。用光学显微镜、原子力显微镜(AFM)及X射线衍射仪对样品进行了表征,结果表明所生长外延层表面无裂纹,并显示出清晰的阶梯流表面形貌,其平均粗糙度为0.160nm,KOH腐蚀坑密度为5.8×108 cm-2,(0002)和(10-12)回摆曲线FWHM分别为210″和396″。详细论述了AlN外延层的生长模式、位错行为和应力释放途径。

Thick 3D buffer layer consisting of low-temperature AlN nucleating layer,medium-temperature, gradual-temperature and high-temperature AlN growth layers was introduced to reduce the dislocation density and release the stress of AlN epitaxial layer grown on sapphire substrate. Optical microscope, atomic force microscopy（AFM） and X-ray diffractometer（XRD）were used to charactertize the samples,and the results indicate that the grown epitaxial layer presents no surface crack and distinct step flow morphology,the root mean square roughnesses（RMS）is 0.160 nm,the KOH etch-pit density is 5.8×108 cm-2,and the fullwidth at half-maximums（FWHM）of X-ray rocking curves（XRC）for（0002）and（10-12）plane is 210″and 396″,respectively.The growth modes,dislocation behaviors and stress release for AlN epitaxial layer were discussed in detail.