Tunable intersublevel transitions in self-forming semiconductor quantum dots

Abstract

Interfacial compositional disordering in ${\mathrm{In}}_{0.6}{\mathrm{Ga}}_{0.4}\mathrm{A}\mathrm{s}/\mathrm{G}\mathrm{a}\mathrm{A}\mathrm{s}$ quantum dots has been used to tune their intersublevel energy spacings $(\ensuremath{\Delta}{E}_{[(i+1)\ensuremath{-}i]}).$ Interdiffusion blueshifted all levels while lowering values for $\ensuremath{\Delta}{E}_{[(i+1)\ensuremath{-}i]}.$ Rate equation simulations of photoluminescence (PL) spectra estimated relaxation lifetime ratios for intersublevel transitions. A slight trend towards increasing thermalization rates at values $\ensuremath{\Delta}{E}_{[(i+1)\ensuremath{-}i]}\ensuremath{\sim}\mathrm{LO}$ phonon energies was found. However, PL measurements showed strong emission from excited states for all $\ensuremath{\Delta}{E}_{[(i+1)\ensuremath{-}i]}$ values, which ranged from 53 to 25 meV.