Lattice strain in bulk GaN epilayers grown on CrN/sapphire template
Lattice strain in bulk GaN epilayers grown on CrN/sapphire template
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DOI：
10.1063/1.3086890
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发表时间：
2009-02-23
影响因子：
4
通讯作者：
Yao, T.
中科院分区：
文献类型：
--
作者：
Lee, S. W.;Ha, Jun-Seok;Yao, T.
利用显微光致发光光谱研究了生长在具有CrN缓冲层的c-蓝宝石上的GaN薄膜的局部应变，其中CrN缓冲层被部分蚀刻。双轴压应变主导生长在CrN缓冲层/c面蓝宝石上的GaN薄膜。当激发激光束从样品的未蚀刻侧扫描到蚀刻侧时，（DX）-X-0、FXA和FXA-1 LO发射线的发射能量从高值逐渐移动到低值，而发射强度仅显示出轻微的变化。在蚀刻过程中，除了GaN膜的分离部分的弯曲从凸到凹的变化之外，在GaN膜中没有发生破裂，如通过表面轮廓仪所确定的。完全分离的GaN的晶格参数和束缚激子发射峰的能量位置几乎与无应变GaN的报道相同。GaN膜的（0002）Ω扫描的线宽通过剥离而从352弧秒变窄至331弧秒，这可能是由于弯曲的减少。这些性质表明，随着CrN缓冲层的蚀刻进行，在CrN缓冲层上生长的GaN层中发生逐渐的晶格应变弛豫，并且化学剥离能够使GaN膜与蓝宝石衬底分离而不产生缺陷。
Microphotoluminescence spectroscopy is used to investigate local strain in GaN films grown on c-sapphire with CrN buffer, where the CrN buffer is partly etched. Biaxial compressive strain dominates GaN films grown on CrN buffer/c-plane sapphire. The emission energies of (DX)-X-0, FXA, and FXA-1LO emission lines shift gradually from a high value to a low one, as the excitation laser beam scans from the unetched side of the sample to the etched side, while the emission intensities show only a slight change. No cracking occurs in the GaN film during etching except a change in bending of the detached part of the GaN film from convex to concave as determined by surface profiler. Both the lattice parameter and the energy position of the bound exciton emission peaks from a completely detached GaN are almost the same as those reported for strain-free GaN. The line width of the (0002) omega scan of a GaN film is narrowed from 352 to 331 arc sec through detaching presumably due to decrease in bending. Those properties suggest that gradual lattice strain relaxation takes place in GaN layers grown on CrN buffer as etching of CrN buffer proceeds and that the chemical lift-off enables to detach a GaN film from a sapphire substrate without generating defects.