VERTICAL MULTIJUNCTION PHOTOVOLTAIC CELLS WITH BURIED SILICIDE INTERCONNECTIONS

WE PROPOSE TO STUDY VERTICAL MULTIJUNCTION CELLS FOR PHOTOVOLTAIC CONVERSION OF HIGH-INTENSITY LASER RADIATION AT 1.06 MICRONS. THE SERIES-CONNECTED MULTIJUNCTION STRUCTURE RESULTS IN LOW SERIES RESISTANCE, WHICH IS CRUCIAL TO EFFICIENT CONVERSION AT THE INTENSITY LEVELS CONTEMPLATED. A SMALL JUNCTION WIDTH, FURTHERMORE, WOULD MAKE POSSIBLE EFFICIENT COLLECTION OF LONG-WAVELENGTH LIGHT WITHOUT A LONG CARRIER DIFFUSION LENGTH, RESULTING IN GOOD RADIATION RESISTANCE. IN ORDER TO ACHIEVE THE SMALL JUNCTION WIDTH (10 TO 20 MICRONS) WHICH IS NEEDED, WE WILL USE ION IMPLANTED SILICIDES FOR THE METAL INTERCONNECTION LAYERS. COSI2, WHICH HAS A HIGH CONDUCTIVITY AND A SMALL LATTICE MISMATCH WITH SILICON, CAN BE FORMED AS A BURIED LAYER BY ION IMPLANTATION OF COBALT AND ANNEALING. HIGH-QUALITY EPITAXIAL SILICON CAN BE GROWN ON THE TOP LAYER AFTER THIS PROCESS. THIN FILMS PRODUCED BY THIS METHOD ARE GENERALLY COHERENT AND UNIFORM AND THEIR INTERFACES ARE SHARP AND FREE FROM CONTAMINATION. IN ADDITION, BURIED SILICIDES ACT AS A GETTER OF THEIR OWN METAL FROM THE BULK SILICON, PREVENTING CONTAMINATION OF THE SOLAR CELL ACTIVE LAYER BY THE IMPLANTED METALS.