9 November 1999 Comparative investigation of high-resolution transmission electron microscopy and Fourier transform infrared spectroscopy for GaN films on sapphire substrate
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Abstract
A comparative study on GaN/sapphire has been performed by transmission electron microscopy (TEM) and IR reflectance (IR). TEM observations reveal that both the undoped and Si doped GaN epilayers have large density of threading dislocations. Dislocations in the undoped GaN tend to from open core structure, while dislocation lines in the Si-doped GaN are very sharp and the strain contrast is much more confirmed. It is believed that Si-doping causes the increase in undoped GaN to much more confirmed dislocation lines. Frank dislocation loops are also found lined up at a depth of about 110 +/- 10 nm from the interface. High resolution TEM study also reveals that the GaN buffer layer grown at low temperature has transformed into its thermodynamically stable wurtzite structure during the high temperature post- buffer GaN epilayer growth process. The comparative IR reflectance hows the corresponding behavior. The interference fringes of the Si doped sample, compared with the undoped ones, shows a contrast damping and reflectance reduction behavior, suggesting the presence of a transition/defect layers near the interface.
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Kun Li, Kun Li, Yong Tian Hou, Yong Tian Hou, Zhe Chuan Feng, Zhe Chuan Feng, Soo-Jin Chua, Soo-Jin Chua, Ming Fu Li, Ming Fu Li, Ernest Lau, Ernest Lau, Andrew Thye Shen Wee, Andrew Thye Shen Wee, "Comparative investigation of high-resolution transmission electron microscopy and Fourier transform infrared spectroscopy for GaN films on sapphire substrate", Proc. SPIE 3899, Photonics Technology into the 21st Century: Semiconductors, Microstructures, and Nanostructures, (9 November 1999); doi: 10.1117/12.369444; https://doi.org/10.1117/12.369444
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