Low density InAs/(In)GaAs quantum dots emitting at long wavelengths

Abstract

We present research carried out on molecular beam epitaxy grown InAs/(In)GaAs quantumdot structures for single-photon operation at long wavelengths. The optical andmorphological properties of the structures are studied as functions of quantum dot growthparameters and of the InGaAs upper confining layer thickness and composition. We showthat low growth rate, high growth temperature and reduced quantum dot coverage arevery effective in reducing the quantum dot density but, owing to In desorptioneffects and quantum dot size reduction, this result is not always concomitant withthe achievement of long wavelength emission. To this aim, we show that the useof InGaAs upper confining layers allows the redshift of quantum dot emissionenergy without affecting their density. Both the thickness and composition ofthe InGaAs layer have to be carefully chosen to provide a complete coverage ofquantum dots and not to exceed the critical thickness for plastic relaxation. Ourresults led to the preparation of quantum dot structures with densities in the low109 cm−2 range,1.33 µm emission at 10 K and full widths at half maximum of 22 meV.