Quantum wells (QWs) are at the heart of opto-electronic devices. Therefore comprehensive characterization of their optical properties is an essential step in device fabrication. Photoluminescence (PL) is a process of emission of light from matter upon excitation by light or photons. As QWs are widely used as LEDs and lasers in opto-electronic devices, PL spectroscopy proves to be a very useful tool in providing information on their size-, structure-and morphology-dependent emission properties.

InGaN/GaN nanostructures are a very important class of semiconductors, being extensively used for fabricating opto-electronics devices operating in the visible spectral range. Several techniques have been developed and perfected for growing InGaN/GaN nanostructures with high degree of purity and uniformity. Though a single QW is an efficient photon emitter, for several applications it is desirable to increase the emitted light intensity by combining the emission from multiple QWs. An important question in device fabrication thus is whether the structural and emission characteristics of QWs depend on the number of QW in a heterostructure? In this Optical Materials Express article, Mounir Mensi et al. used an advanced form of PL spectroscopy based on a near-field scanning microscope to achieve extremely high spatial resolution and reveal the influence of the number of QWs on PL properties and their spatial variation.

The detailed experimental investigations performed by the authors show that there is no additional broadening or shift of the PL spectra in the multiple InGaN/GaN QWs, consisting of several QWs compared to the single QW structure. The results indicate that the wells in multiple QW structures grown by metal organic chemical vapour deposition technique are nearly identical. The fluctuations in the structure and composition of an individual well do not affect their optical response. The authors observed no shift in the spectral position or changes in the spectral width even for the heterostructures consisting of 10 QWs. Their results suggest that using a large number of QWs in the active region of semipolar light emitters is a promising way to increase the emission intensity.

The systematic studies presented by the authors will shed new light on the relationship between the number and optical response of InGaN/GaN QWs, which may lead to development of novel opto-electronic devices.

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