Microcrack-induced strain relief in Ga N ∕ Al N quantum dots grown on Si(111)

The optical properties of vertically stacked self-assembled $\mathrm{Ga}\mathrm{N}∕\mathrm{Al}\mathrm{N}$ quantum dots (QD's) grown on Si substrates were studied by means of temporally and spatially resolved cathodoluminescence (CL). An analysis of the CL spectra, thermal activation energies, and measured decay times of the QD luminescence was performed near stress-induced microcracks, revealing changes in the optical properties that can be attributed to stress-dependent variations in the band edges, the polarization field, and the oscillator strength between electrons and holes. Three-dimensional $6\ifmmode\times\else\texttimes\fi{}6$ $\mathbit{k}∙\mathbit{p}$ calculations of the QD electron and hole wave functions and eigenstates were performed to examine the influence of biaxial and uniaxial stresses on the optical properties in varying proximity to the microcracks.