1.3 MICRON IN(ALGA)AS PHOTOVOLTAIC LASER ENERGY CONVERTERS

THIS PROJECT WILL INVESTIGATE UNIQUE LASER-ENERGY CONVERTERS(LECS) FOR 1.315 MICRON (0.943 EV) IODINE LASER, SPACE POWERSYSTEMS. THE GOAL IS TO CONVERT 40-50 PERCENT OF THE INCIDENT LASER POWER OF 500-1000 W/CM(2) TO ELECTRICAL POWER. TO ACHIEVE THE OPTIMUM 0.94 EV BANDGAP, METALORGANIC CHEMICAL VAPOR DEPOSITION (MOCVD) OF AN INNOVATIVE COMPOUND SEMICONDUCTOR, LN0.53(ALXGA1-X)0.47. AS, LATTICE-MATCHED TO INP SUBSTRATES, IS PLANNED. THE BANDGAP OF IN0.53GA0.47. AS (0.75 EV), LATTICE-MATCHED TO INP, IS SUBOPTIMAL; HOWEVER, BY ADDING AL TO THE INGAAS SO THAT THE ALXGA1-X FRACTION STAYS AT 0.47, THE LATTICE MATCH TO INP IS MAINTAINED AT THE SAME TIME AS THE EPILAYER BANDGAP INCREASES. INITIAL CALCULATIONS INDICATE IN0.53AL0.13GA0.34AS HAS THE OPTIMUM 0.94 EV BANDGAP. AN INNOVATIVE, PLANAR, SERIES-CONNECTED, MULTIJUNCTION LEC SHOULD LIMIT SERIES RESISTANCE EFFECTS. A PLANAR APPROACH AVOIDS SOME OF THE PROCESSING PROBLEMS INHERENT IN VERTICAL MULTIJUNCTION DESIGNS. IN PHASE I, IN0.53GA0.47. AS (CONTROL) AND IN0.53AL0.13GA0.34. AS PROTOTYPE LAYERS WILL BE GROWN ON INP SUBSTRATES WITH INP WINDOWS. THE BANDGAPS WILL BE CHECKED BY PHOTOLUMINESCENCE, THE LATTICE MATCH BY X-RAY DIFFRACTOMETRY, AND THE DOPING BY CV PROFILING. CELLS WILL BE FABRICATED TO CHECK THE PN JUNCTIONS AND TO MEASURE THE LOG IV, QUANTUM EFFICIENCY, AND POWER-CONVERSION EFFICIENCY. PLANAR, MULTIJUNCTION LEC WILL BE DESIGNED USING MEASURED DATA FROM THE ACTUAL MATERIAL, WITH PARTICULAR ATTENTION PAID TO ATTAINING A LOW SERIES RESISTANCE AND HIGH EFFICIENCY. IN PHASE II, FULL-SIZED, OPTIMIZED, PLANAR, SERIES-CONNECTED MULTIJUNCTION LECS BASED ON THE PHASE I WORK WOULD BE GROWN, FABRICATED, AND TESTED. THIS PROJECT WILL INVESTIGATE UNIQUE LASER-ENERGY CONVERTERS(LECS) FOR 1.315 MICRON (0.943 EV) IODINE LASER, SPACE POWERSYSTEMS. THE GOAL IS TO CONVERT 40-50 PERCENT OF THE INCIDENT LASER POWER OF 500-1000 W/CM(2) TO ELECTRICAL POWER. TO ACHIEVE THE OPTIMUM 0.94 EV BANDGAP, METALORGANIC CHEMICAL VAPOR DEPOSITION (MOCVD) OF AN INNOVATIVE COMPOUND SEMICONDUCTOR, LN0.53(ALXGA1-X)0.47. AS, LATTICE-MATCHED TO INP SUBSTRATES, IS PLANNED. THE BANDGAP OF IN0.53GA0.47. AS (0.75 EV), LATTICE-MATCHED TO INP, IS SUBOPTIMAL; HOWEVER, BY ADDING AL TO THE INGAAS SO THAT THE ALXGA1-X FRACTION STAYS AT 0.47, THE LATTICE MATCH TO INP IS MAINTAINED AT THE SAME TIME AS THE EPILAYER BANDGAP INCREASES. INITIAL CALCULATIONS INDICATE IN0.53AL0.13GA0.34AS HAS THE OPTIMUM 0.94 EV BANDGAP. AN INNOVATIVE, PLANAR, SERIES-CONNECTED, MULTIJUNCTION LEC SHOULD LIMIT SERIES RESISTANCE EFFECTS. A PLANAR APPROACH AVOIDS SOME OF THE PROCESSING PROBLEMS INHERENT IN VERTICAL MULTIJUNCTION DESIGNS. IN PHASE I, IN0.53GA0.47. AS (CONTROL) AND IN0.53AL0.13GA0.34. AS PROTOTYPE LAYERS WILL BE GROWN ON INP SUBSTRATES WITH INP WINDOWS. THE BANDGAPS WILL BE CHECKED BY PHOTOLUMINESCENCE, THE LATTICE MATCH BY X-RAY DIFFRACTOMETRY, AND THE DOPING BY CV PROFILING. CELLS WILL BE FABRICATED TO CHECK THE PN JUNCTIONS AND TO MEASURE THE LOG IV, QUANTUM EFFICIENCY, AND POWER-CONVERSION EFFICIENCY. PLANAR, MULTIJUNCTION LEC WILL BE DESIGNED USING MEASURED DATA FROM THE ACTUAL MATERIAL, WITH PARTICULAR ATTENTION PAID TO ATTAINING A LOW SERIES RESISTANCE AND HIGH EFFICIENCY. IN PHASE II, FULL-SIZED, OPTIMIZED, PLANAR, SERIES-CONNECTED MULTIJUNCTION LECS BASED ON THE PHASE I WORK WOULD BE GROWN, FABRICATED, AND TESTED.