USE OF DOUBLE BAND ANTI-CROSSING TO CONTROL OPTICAL ABSORPTION OF GAASSBN FOR MULTI-JUNCTION SOLAR CELLS

摘要

Dilute nitride materials such as GaAsSbN offer the possibility for large changes in bandgap with relatively small variation of the nitrogen content and can meet the requirement for a 1 eV bandgap lattice-matched to GaAs. In a multi-junction solar cell, the precise combination of bandgaps is an important factor for increasing efficiency and must be optimised to the incident spectrum. GaAsSbN is particularly interesting as Sb affects the valence band and N affects the conduction band independently through separate band anti-crossing interactions. These interactions split their respective bands and have been seen to increase the electron effective mass in dilute nitride alloys. We discuss the effects of Sb and N composition on the band structure and use a model dielectric function to determine the factors that control the absorption coefficient of the material.