Spectroscopic ellipsometry study on the electronic structure near the absorption edge of GaAsN alloys

Spectroscopic ellipsometry has been used to investigate the electronic stru cture near the fundamental absorption edge of GaAsN alloys grown by metalor ganic vapor phase epitaxy. The fundamental absorption edge is clearly obser ved in the imaginary part of the dielectric function and shifts to lower en ergies with increasing N concentration. In addition, the absorption structu re is observed near the E-0 gap energy of GaAs even in GaAsN alloys. This u nequivocally shows that the fundamental absorption edge of GaAsN is not shi fted from the E-0 gap of GaAs but newly formed by the N incorporation. Thus . the formation of the narrowest band gap of GaAsN alloys is found to be co mpletely different from that of conventional compound semiconductor alloys, such as AlGaAs and GaAsP.