Matrix dependence of strain-induced wavelength shift in self-assembled InAs quantum-dot heterostructures

We report on the matrix-dependent strain effect in self-assembled InAs quantum-dot heterostructures using photoluminescence measurements. A series of samples were prepared to examine the effect of quantum dot position with respect to the so-called strain-reducing layer (SRL). Since the SRL reduces the residual hydrostatic strain in the quantum dots, long emission wavelength of 1.34 μm is observed for the InAs quantum dots with an ${\mathrm{In}}_{\mathrm{0.16}}{\mathrm{Ga}}_{\mathrm{0.84}}\mathrm{As}$ SRL. The dependence of the emission wavelength on the thickness of the cap layer on SRL also indicates the importance of the role of matrix in the strain relaxation process of the dots. Using ${\mathrm{In}}_{\mathrm{0.16}}{\mathrm{Al}}_{\mathrm{0.84}}\mathrm{As}$ instead of ${\mathrm{In}}_{\mathrm{0.16}}{\mathrm{Ga}}_{\mathrm{0.84}}\mathrm{As}$ as the SRL, a blueshift in wavelength is observed because the elastic stiffness of ${\mathrm{In}}_{\mathrm{0.16}}{\mathrm{Al}}_{\mathrm{0.84}}\mathrm{As}$ is higher than that of ${\mathrm{In}}_{\mathrm{0.16}}{\mathrm{Ga}}_{\mathrm{0.84}}\mathrm{As}$ and less strain is removed from the dots with ${\mathrm{In}}_{\mathrm{0.16}}{\mathrm{Al}}_{\mathrm{0.84}}\mathrm{As}$ SRL.