Strain-engineered InAs/GaAs quantum dots for long-wavelength emission

Using a combination of a seed layer, low-growth rates, and different growth temperatures, we have produced InAs/GaAs quantum dots (QD’s) that emit at very long wavelengths (up to $1.39\mu \mathrm{m}$ at 293 K) with an ultranarrow inhomogeneous broadening (full width at half maximum of 14 meV at 10 K). The results are discussed in terms of strain relaxation and reduced In/Ga intermixing in the second layer. These two phenomena are interrelated and their control is crucial for achieving long wavelength emission. The QD structures also exhibit interlayer electronic coupling effects. Finally, combining this method with the use of InGaAs in the barrier instead of GaAs, emission wavelengths around $1.5\mu \mathrm{m}$ at 293 K have been achieved.