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 $\left(\Delta E_{\left[\mathrm{}\right(i+1\mathrm{}\left)\mathrm{}-i\right]}\right).\mathrm{}$ Interdiffusion blueshifted all levels while lowering values for $\Delta E_{\left[\mathrm{}\right(i+1\mathrm{}\left)\mathrm{}-i\right]}.$ Rate equation simulations of photoluminescence (PL) spectra estimated relaxation lifetime ratios for intersublevel transitions. A slight trend towards increasing thermalization rates at values $\Delta E_{\left[\mathrm{}\right(i+1\mathrm{}\left)\mathrm{}-i\right]}\sim \mathrm{LO}$ phonon energies was found. However, PL measurements showed strong emission from excited states for all $\Delta E_{\left[\mathrm{}\right(i+1\mathrm{}\left)\mathrm{}-i\right]}$ values, which ranged from 53 to 25 meV.