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The enhancement in luminescence property of chemically passivated near surface quantum well and quantum dots

Epitaxially grown III-As nanostructures, like quantum well (QW)/ quantum dot (QD) have already been scrutinized rigorously and incorporated into various devices, like light-emitting diode (LED), laser, Photodetector, solar cell, etc. Most of them use buried QW/QD heterostructure, where the as-grown nanostructures are capped with various combination of thick (In/Ga/Al)As matrix. In contrary, near-surface nanostructures have very less attention owing to additional surface states. However, these near-surface nanostructures have the potential to communicate with the external world. Therefore, it might act as a confined channel, which can be probed externally. Assertively, these near -surface nanostructures have immense potential to act as sensors. Before that, we need to passivate the surface states to hold the best communication with the outer environment. In the present study, we have used Thiourea as a source of sulfur and show the effect of passivation in terms of improved luminescence behavior. Near-surface GaAs/In0.15Ga0.85As/GaAs quantum well and self-assembled GaAs/InAs/GaAs SK quantum dots are grown on GaAs wafer through molecular beam epitaxy. The effective thickness of the top GaAs capping layer has been kept around eight nanometers and twelve nanometers to keep the nanostructure (QW/QD) very close to the surface. As grown samples have shown very poor photoluminescence peaks and increased by few orders after passivation. Pre-etching followed by sulfur passivation has shown the best enhancement of luminescence intensity.