Substrate orientation effects on quantum dot enhanced GaAs solar cells

The state of the art in space solar cells utilizes epitaxially grown III-V multijunction cells with champion devices exceeding 30% efficiency under 1-sun. An array of self-organized InAs quantum dots (QD) within a GaAs matrix is one approach to enable significant efficiency improvements by extending the spectral bandwidth of the GaAs cell. In this paper, the effect of substrate misorientation away from (100) on QD epitaxy and on QD-enhanced GaAs solar cells was investigated. The use of offcut samples (up to 6 degrees) leads to very low PL. However, the QD-enhanced GaAs solar cells grown on the 6° to [111] oriented substrate exhibit the highest Voc. The results suggest that vicinal substrates modify the recombination properties of QD-enhanced solar cells.