Dual junction GaInP/GaAs solar cells grown on metamorphic SiGe/Si substrates with high open circuit voltage

Abstract

Dual junction GaInP/GaAs solar cells have been grown and fabricated on Si substrates using relaxed, compositionally graded SiGe buffer layers that provide a nearly lattice-matched low threading dislocation Ge surface for subsequent cell growth. The dual junction cells on SiGe/Si displayed high open circuit voltages in excess of 2.2 V, compared to 2.34 V for control cells on GaAs, that are consistent with maintaining the 1.8/spl times/10/sup 6/ cm/sup -2/ threading dislocation density throughout the cell structure. Even with total current output limited by large grid coverage and high reflectance, total area AM1.5G efficiency is 16.8%, with active area efficiency at 18.6%. The high V/sub oc/ establishes that SiGe metamorphic buffers are viable for integrating III-V multijunction cells on Si in a monolithic process.