III-V Solar Cells Grown Directly on V-groove Si Substrates

We report on the development of GaAs solar cells directly grown on nanopatterned V-groove Si substrates by metalorganic vapor-phase epitaxy (MOVPE). A low threading dislocation density (TDD) of 3×106 cm-2 was achieved in the GaAs through a combination of thermal cycle annealing and InGaAs dislocation filter layers. Front junction GaAs solar cells were then grown on these low-TDD substrates, but preliminary devices produced a conversion efficiency of only 6.6% without an anti-reflection coating. Electron channeling constast imaging measurements on this cell showed a high density of misfit dislocations at the interface between the AlInP/GaInP window layer and GaAs absorber, likely causing poor surface passivation and thus poor performance. The source of these misfit dislocations will be discussed, as well as mitigation strategies to improve solar cell performance.