Comparative studies of band structures for biaxial (100)-, (110)-, and (111)-strained GeSn: A first-principles calculation with GGA+U approach

摘要: Experiments and calculations performed in previous studies indicate that compressive strain will increase (100)-strained GeSn's need for Sn to realize a direct bandgap when it is pseudomorphically grown on Ge buffers. To eliminate this negative effect, we systematically investigate the band structures of biaxial (100)-, (110)-, (111)-strained GeSn using first-principle calculation combined with supercell models GGA+U approach. This method has proven be efficient accurate calculating properties GeSn. The calculated lattice constants elastic are good agreement experimental results. crossover value concentration which required change unstrained from indirect found 8.5%, very close recent result 9%. bandgaps strained show moving rate Γ valley higher than those L X valleys (100)- (110)-strained However, Tensile positive effect transition GeSn, changing direct, whereas use (111) orientation can reduce greatly energy difference between valley. Thus, buffers, choice take advantage strain.