Effect of barrier composition and well number on the dark current of quantum well solar cells

The effect of raising the barrier band-gap and the number of wells on the dark current of MOVPE-grown GaAs/sub 1-x/P/sub x//In/sub y/Ga/sub 1-y/As strain-compensated multi-quantum well (MQW) solar cells is investigated. Increasing the number of wells increases the photocurrent linearly, whereas the dark current increases sub-linearly. These results enable us to demonstrate a 50 well strain-compensated cell that has a higher efficiency than a comparable previously published GaAs p-i-n cell and a p-n grown in the same MOVPE machine. Increasing the phosphorus content of the barriers increases dark current but also causes some morphological changes, which are attributed to step bunching during growth. This has been remedied by reducing the growth temperature of the MQW region.