Carrier sweep-out time in InGaAs/GaAsP multiple quantum well solar cells by time-resolved photoluminescence: effects of well depth and barrier thickness

Sweep-out times for cross-well transport in p-i-n GaAs solar cells containing 20-period of InGaAs/GaAsP multiple quantum wells were evaluated by biased time-resolved photoluminescence. Effects of InGaAs well depth and GaAsP barrier thickness were analyzed and compared with simulation of carrier escape times from a single quantum well in a presence of an electric field. The tendencies and relative values of calculated escape rates suggested that the effective barrier height is the most important parameter to determine the carrier escape times in a quantum well. The dominant transport mechanism for the MQW in this work is most likely the thermionic emission from electron ground states followed by thermal assisted tunneling depending on the structure. In order to extend the absorption edge of the MQWs while keeping strain balance, thick GaAsP barriers with a small P content is preferable in the viewpoint of carrier extraction.