IMPROVED QUANTUM EFFICIENCY IN GASB/GAAS HETEROJUNCTION PHOTOVOLTAIC CELLS USING AN OFFSET P-N JUNCTION

摘要

The external quantum efficiency of GaSb/GaAs heterojunction TPV cells has been enhanced by using a thin n-GaSb buffer layer between the n-GaAs and the p-GaSb to offset the p-n junction from the heterojunction. All samples were grown by MOVPE at temperatures of 590°C. Cells with the p-n junction displaced from the heterojunction showed a significant improvement in photoresponse and open circuit voltage (VOC). Short circuit current (ISC) was also increased by addition of a thin n-GaSb layer (～100nm) but little or no improvement resulted if the n-GaSb layer thickness was further increased. For the growth conditions and doping levels in this set of samples a displacement of the p-n junction from the heterojunction of around 400nm was sufficient to achieve maximum enhancement in performance.