Defect reduction in Si-doped Al0.45Ga0.55N films by SiNx interlayer method
Defect reduction in Si-doped Al0.45Ga0.55N films by SiNx interlayer method
复制标题
DOI：
10.1063/1.4862804
复制
发表时间：
2014-01-28
影响因子：
3.2
通讯作者：
Chen, Changqing
中科院分区：
文献类型：
--
作者：
Li, Yang;Chen, Shengchang;Chen, Changqing
本研究通过引入原位沉积的SiNx纳米掩模层，有效降低了在蓝宝石衬底上生长的Al含量高达45%的AlGaN外延层的位错密度。通过密切监测Si-Al0.45Ga0.55N层的众多材料特性（例如表面形貌、位错密度、光致发光、应变状态和电子迁移率）随SiNx层间生长时间的变化，发现SiNx的表面覆盖率是决定应变状态和位错密度的关键因素。应变状态和位错密度对 SiNx 纳米掩模表面覆盖率的依赖性支持了 SiNx 中间层上富铝 AlGaN 的非常不同的生长模型，因为与 GaN 对应物相比，其成核选择性降低。与只能在 SiNx 纳米掩模的开孔处成核的 GaN 相比，富铝 AlGaN 可以同时在开孔和 SiNx 覆盖区域成核。由于开口区域开始的 3D 生长，位错将在开口处消失，而 SiNx 上保留了 2D 生长模式，并且螺纹位错也被保留。在接下来的生长过程中，横向过度生长将从开口上的Al0.45Ga0.55N岛向SiNx覆盖的区域进行，同时松弛压应变并弯曲位错。 (C) 2014 AIP 出版有限责任公司。
The dislocation density in AlGaN epitaxial layers with Al content as high as 45% grown on sapphire substrates has been effectively reduced by introducing an in-situ deposited SiNx nanomask layer in this study. By closely monitoring the evolution of numerous material properties, such as surface morphology, dislocation density, photoluminescence, strain states, and electron mobility of the Si-Al0.45Ga0.55N layers as the functions of SiNx interlayer growth time, the surface coverage fraction of SiNx is found to be a crucial factor determining the strain states and dislocation density. The dependence of the strain states and the dislocation density on the surface coverage fraction of SiNx nanomask supports the very different growth models of Al-rich AlGaN on SiNx interlayer due to the reduced nucleation selectivity compared with the GaN counterpart. Compared with GaN, which can only nucleate at open pores of SiNx nanomask, Al-rich AlGaN can simultaneously nucleate at both open pores and SiNx covered areas. Dislocations will annihilate at the openings due to the 3D growth initiated on the opening area, while 2D growth mode is preserved on SiNx and the threading dislocations are also preserved. During the following growth process, lateral overgrowth will proceed from the Al0.45Ga0.55N islands on the openings towards the regions covered by SiNx, relaxing the compressive strain and bending the dislocations at the same time. (C) 2014 AIP Publishing LLC.