Efficient carrier injection in strain-free mesoscopic GaAs structures

The fabrication of strain-free mesoscopic GaAs structures (MGS) by Ga-assisted droplet etching (see sketch below) has attracted attention of the scientific community due to the excellent optical emission characteristics with sharp emission lines associated to different excitonic states. One way to expand the MGS application perspectives is to explore band structure engineering. In this sense, type-II band-alignment offers an additional degree of freedom in order to modify the light emitting properties of this type of semiconductor nanostructure. However, the induced spatial separation between electron and hole wavefunctions has been demonstrated to lead to considerable quenching of photoluminescence (PL) emission in quantum rings grown by droplet epitaxy.

 In this work, we show that, by changing the Al concentration, we can modify the intensity and the energy range of the optical emission of the MGS. We show that, in comparison to previous works, MGS emission can be enhanced by up two orders of magnitude by controlling the coupling of the MGS with a neighboring quantum well. We present Al-rich structures with high emission intensity and long/tunable carrier lifetimes which can be interesting for future applications in solid-state optoelectronic devices and solar cells.

This work was done in collaboration with Prof. Christoph Deneke from IFGW and Prof. Leonarde Rodrigues from the University of Viçosa (UFV).

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