材料科学
成核
外延
透射电子显微镜
光电子学
图层(电子)
亚稳态
缓冲器(光纤)
锌
结晶学
纳米技术
化学
冶金
计算机科学
电信
有机化学
作者
Sung Bo Lee,Tae-Wan Kwon,Jungwon Park,Won Jin Choi,Hae Sung Park
标识
DOI:10.1016/j.jcrysgro.2012.04.036
摘要
In the present study, we show the formation of mushroom morphology produced by a ramp anneal of a low-temperature GaN buffer layer. Structural analysis by transmission electron microscopy indicates that the cap of the mushroom has the stable wurtzitic GaN structure, whereas the stem possesses the metastable zinc-blende structure. With the air gap introduced between the substrate and the cap of the mushroom structure, threading dislocations propagate along its stem. The formation of the mushroom morphology is suggested to result from the nucleation of wurtzitic GaN on the surface of the low-temperature buffer layer during the ramp anneal, followed by mass transport of GaN from the buffer layer, which remains zinc-blende during the anneal, to the surface, because wurtzitic GaN has the lower structure energy than zinc-blende GaN. This study extends limits of the conventional use of the buffer layer, laying the foundation for the development of low-cost recipes for achieving GaN templates with a low density of threading dislocations.
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