Role of nitrogen precursor supplies on InAs quantum dot surfaces in their emission wavelengths

The role of nitrogen (N) in emission wavelengths from InAs quantum dots (QDs) was studied with intentional supplies of a N precursor (monomethylhydrazine) to InAs dot surfaces just before burying them with GaAs capping layers by metalorganic molecular-beam epitaxy. Luminescence from the InAs QDs showed a red shift with the N-precursor supplies on the dot surfaces, and more clear separations of the luminescence sub peaks originating from QD excited-state transitions were observed. The increase in the N precursor supplies on the dot surfaces however changed the relative variation in the emission wavelengths from the red shift to the blue shift. Additional observations of the dot sizes as well as the model calculations of the emission peaks and of the energy separations of the lowest and QD excited-state transitions showed that the red shift is due to the reduced Ga inclusion in the InAs QDs and that the blue shift is due to the reduced dot sizes.