GaInNAs for multi-junction tandem solar cells

We have investigated the effect of atomic H irradiation on the growth of GaInNAs/GaAs films in hydrogen-assisted RF-molecular beam epitaxy (RF-MBE) from the viewpoint of growth dynamics and material quality. The crystal quality of GaInNAs films was characterized by using X-ray diffraction (XRD) and photoluminescence (PL), and the surface morphology was characterized by using atomic force microscope (AFM). The atomic H irradiation during the growth of GaInNAs was found to be very effective in improving the overall quality of epilayers. Further, we found that atomic H irradiation acts to suppress 3-dimensional islanded growth, and promote a 2-dimensional growth mode. Atomic H was also effective in passivating the active recombination defect centers. An improved PL characteristics was observed for GaInNAs grown on GaAs with atomic H at /spl sim/1.0 eV, measured at 77 K. In addition, we have also investigated the growth of GaInNAs films on Ge substrates, which is attractive for use in multi-junction III-V tandem solar cells.