High-quality thin film GaAs bonded to Si using SeS2 — A new approach for high-efficiency tandem solar cells

Epitaxial GaAs thin-films grown by metal organic chemical vapour deposition technique have been successfully bonded to Si substrates and lifted-off from the original GaAs substrate using the epitaxial lift-off (ELO) technique. The GaAs thin films transplanted in this manner to Si substrate were examined for its quality by photoluminescence, double-crystal X-ray diffraction and Raman scattering studies. The low FWHM, no peak energy and peak frequency shift were associated with the high crystalline quality of the bonded films. We have obtained a minority-carrier lifetime of 9.09 ns in a double heterostructure bonded to Si, which is nearly three times higher than heteroepitaxial GaAs on Si. The electron transport across the bonded interface was studied by observing the current–voltage characteristic. The electrical behaviour was improved by applying a voltage greater than 10 V, necessary for current conduction.