The Study of Energy Band Gap of In_xAl_yGa_(1-x-y)N Quaternary Alloys using UV-VIS Spectroscopy

摘要

Quaternary In_xAl_yGa_(1-x-y)N alloys with indium (In) mole fraction x ranging from 0.01 to 0.10 and constant aluminum (Al) mole fraction y = 0.06, were grown by molecular beam epitaxy. The energy band gaps of InAlGaN alloys were investigated using UV-VIS spectroscopy under room temperature. The energy band gap decreases with increasing In composition from 0.01 to 0.08. This trend is expected since the incorporation of In lowers the energy band gap of Al_(0. 06)Ga_(0.940N (3.72 eV). However, for InAlGaN with In composition of 0.1, the band gap shows a sudden increase in energy. This is probably due to local alloy compositional fluctuations in the epilayer, contributed by incomplete substitutions of Ga atoms by the In atoms, thus retaining a much richer GaN structure. Finally, we investigate the bowing parameter appears also to be very sensitive on In content. We obtained b = 50.08 for quaternary InAlGaN alloys.