Metamorphic GaAsP Tunnel Junctions for High-Efficiency III–V/IV Multijunction Solar Cell Technology

Metamorphic GaAs _0.9 P _0.1 tunnel diodes, designed for application to heteroepitaxial GaInP/GaAsP/Si multijunction solar cells, were grown on compositionally graded GaAs _y P _1-y /GaAs buffers by molecular beam epitaxy. Optimal growth conditions for high impurity doping were determined and tested using fabricated tunnel diode structures. Peak current densities of 103.9 A · cm ^-2 and resistance-area products of 4.5 × 10 ^-4 Ω · cm ² were obtained. Strong agreement between simulated and fabricated devices indicates excellent device quality with respect to optimized growth conditions and near-nominal operation. These results suggest that the optimized structures are promising for use within III-V/Si multijunction solar cells operating under high concentration.