Photoluminescence (PL) at wavelengths over 1.55 μm from self-assembled InAs quantum dots (QDs) grown on GaAs(001) is observed at room temperature (RT) and 4 K using a bilayer structure with thin cap. The PL peak has been known to redshift with decreasing cap layer thickness, although accompanying intensity decrease and peak broadening. With our strain-controlled bilayer structure, the PL intensity can be comparable to the ordinary QDs while realizing peak emission wavelength of 1.61 μm at 4 K and 1.73 μm at RT. The key issue lies in the control of strain not only in the QDs but also in the cap layer. By combining with underlying seed QD layer, we realize strain-driven bandgap engineering through control of strain in the QD and cap layers.

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