Localized strain reduction in strain-compensated InAs∕GaAs stacked quantum dot structures

The authors report the effect of localized strain in stacked quantum dots (QDs) with strain-compensation (SC) layers by evaluating the vertical coupling probability of QD formation between stacks measured as a function of spacer thickness. The localized strain field induced at each QD can be partially suppressed by SC layers, resulting in reduced coupling probability with moderate spacer thickness along with the improved QD uniformity and optical properties. The authors have simulated the local strain field along with subsequent QD formation and coupling probability based on a distributed surface chemical potential. By fitting the experimentally derived coupling probability to the modeled values, a 19% reduction of the localized strain field is obtained for the SC structures compared to the uncompensated structures.