GaAs/Si solar cells with internal Bragg reflector superlattice structure

The characterization of thin film GaAs/Si solar cells grown by low-temperature molecular beam epitaxy (MBE) is presented. With assistance of atomic hydrogen irradiation in MBE, a clear streak RHEED pattern and sharp PL spectra with FWHM of less than 10 meV at 77 K were obtained. It was found that GaAs/Si layers grown at low temperatures were strained, and were gradually relaxed with increasing layer thickness. Bragg reflector superlattice structure was introduced into GaAs/Si solar cells. A remarkable improvement of spectral response was observed in the bandedge region of 790 nm /spl sim/ 840 nm, which is often degraded in a typical GaAs/Si solar cell. Suppression of threading dislocations owing to both lattice mismatch and thermal expansion coefficient difference was observed, as a result of insert ion BR superlattice structures and low-temperature growth.