Control of weakly localized states in semiconductor quantum structures through modification of roughness and composition in the barrier layers

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Near-field photoluminescence imaging spectroscopy of the wetting layer of InAs/InP quantum dot (QD) at the critical thickness (2.4 monolayer (ML)) was conducted to visualize spatial variation in interface disorder. Compared to the result obtained from an InAs/InP quantum well (2 ML thickness), the density of carrier localization center in the wetting layer was found to be significantly reduced, preferably in the vicinity of QDs. The result indicates that short-range interface disorder was smoothed out at the beginning of QD formation. To the contrary, far apart from the QDs, atomic scale disorder still remained.