Optical dielectric function and electronic band structure of dilute GaAsBi-GaAs multiquantum wells by using variable angle spectroscopic ellipsometry

Abstract

ObjectivesThis letter reports about the electronic band structure of dilute GaAsBi-GaAs quantum wells (QWs) experimentally studied by variable angle spectroscopic ellipsometry (VASE) and theoretically by nextnanomat software by solving symmetric double quantum well. MethodologyThe GaAsBi-GaAs quantum wells (QWs) samples were grown by molecular beam epitaxy (MBE). X-Ray diffraction (XRD) measurements were performed to confirm the incorporation of Bismuth in GaAs. Raman measurements in all samples were performed to investigate the lattice vibration properties. Spectroscopic ellipsometry was used first time on bismide quantum wells to estimate the optical functions and critical point transition energies of the innovative GaAsBi quantum wells. A parameterized semiconductor model was used to demonstrate the dielectric function of alloys as a combination of Gaussian oscillators focused on critical points in the band structure. Then from this model, energy values of those critical points are extracted. ResultsThe bandgap was measured for QWs samples for a range of bismuth concentration (1 %, 2 % and 3 %) and bulk sample with Bismuth concentration 0 % and 5 %. PL measurements of bulk and quantum wells samples showed reduction in bandgap with the increase in Bismuth concentration. This reduction in bandgap for QW samples was also confirmed experimentally by VASE and theoretically by using nextnanomat software. ConclusionThis research work gives important electronic and optical parameters for the Bismide quantum wells to design optoelectronic devices using these innovative alloys.