Tuning quantum dot properties by activated phase separation of an InGa(Al)As alloy grown on InAs stressors

Strain-driven decomposition of an alloy layer is investigated as a means to control the structural and electronic properties of self-organized quantum dots. Coherent InAs/GaAs islands overgrown with an InGa(Al)As alloy layer serve as a model system. Cross-section and plan-view transmission electron microscopy as well as photoluminescence (PL) studies consistently indicate an increase in height and-width of the island with increasing indium conten t and/or thickness of the alloy layer. The increasing island size is attrib uted to the phase separation of the alloy layer driven by the surface strai n introduced by the initial InAs islands. The decomposition is enhanced by the addition of aluminum to the alloy layer. The ground-state transition en ergy in such quantum dots is significantly (up to 200 meV) redshifted compa red to the original InAs/GaAs quantum dots, allowing to reach the 1.3 mum s pectral region maintaining the high PL efficiency and the low defect densit y typical for Stranski-Krastanow growth. The possibility of degradation les s stacking of such quantum dot layers enables injection lasing on the groun d-state transition with a differential efficiency of 57% and a continuous-w ave output power of 2.7 W.