Tuning the optical properties of InAs QDs by means of digitally-alloyed GaAsSb strain reducing layers

In this work, we demonstrate the use of a digitally alloyed GaAsSb as a strain reducing layer (SRL) to tune the optical properties of InAs quantum dots grown on GaAs substrates. The GaAsSb digital alloy was made using a short period GaAs/GaSb superlattice. Increasing the Sb-shutter duty cycle (Sb-SDC) from 0 to 0.35 redshifts the emission wavelength from 1220 nm to 1492 nm at 300 K. The wavelength red shift is attributed mainly to the increased Sb content in the GaAsSb SRL as confirmed by high resolution X-ray diffraction. Power dependent photoluminescence showed a type II band alignment for the samples grown with a Sb-SDC of 0.25 and 0.35. Reversing the growth order of GaAs and GaSb layers and maintaining the same Sb-SDC (0.25) drastically alters the optical properties of the QDs. A large wavelength blue shift of 143 nm and a transformation from a type II to type I emission were observed as a result of GaSb intermixing with InAs QDs.