Resonant depletion of photogenerated carriers in InGaAs/GaAs nanowire mats

Photoluminescence excitation spectra of InGaAs in InGaAs/GaAs heterostructure nanowire mats show clear antiresonances at the critical points of the joint density of states of the GaAs barrier. This remarkable effect arises from resonant light absorption in the upper GaAs segments, with ensuing reduction of photogenerated carriers reaching the lower InGaAs segments. The extent of this effect depends strongly on the excitation geometry of the wires, as well as on their areal density. Our work suggests that a careful design is required for optimal light conversion in nanowire-based solar cell devices.