Evolution of the Shape and Size of Ingaas Selforganized Quantum Dots

We have found a shape transformation of InGaAs quantum dots formed via a fractional monolayer deposition technique on GaAs (001) surfaces. This is evidenced by the bimodal quantum dot height (peaked at 8.5 nm and 14.5 nm) and aspect ratio (peaked at 0.18 and 0.26) distributions. The lateral size, height, and aspect ratio all become convergent, suggesting a simultaneous quantum dot size equalization and shape stabilization. Photoluminescence peaks red shift as a consequence of dot growth, and their line-widths become smaller due to dot shape stabilization and size equalization. A record low inhomogeneous broadening of 18.4 meV at a wavelength of 1180 nm (4 K) is obtained for vertically-aligned, shape-stabilized, and size-equalized InGaAs dots.