InAs/GaNAs strain-compensated quantum dots stacked up to 50 layers for use in high-efficiency solar cell

We have investigated the effect of strain compensation on the structural and optical properties of multiple stacked InAs quantum dots (QDs) on GaAs (0 0 1) substrates grown by atomic hydrogen-assisted RF-MBE. Strain relaxation was not observed from the reciprocal space mapping, and as a result, dislocations and coalesced islands were not observed in 50 layer-stacked QDs. Thus, the total QD density of as high as 2.5×1012 cm−2 was achieved. For QD solar cell characterization, the short-circuit current density increased from 21.0 to 26.4 mA/cm2 as the number of stacks was increased from 20 to 50. Further increase of stacks did not affect the open-circuit voltage of ∼0.7 V and diode factor of ∼1.6, which implies that high crystalline quality was maintained even after 50 layers of stacking.