Nature of the optical transition in (In,Ga)As(N)/GaP quantum dots (QDs): Effect of QD size, indium composition and nitrogen incorporation

The structural properties of (In,Ga)As/GaP quantum dots (QDs) are studied by plane view and cross scanning tunneling microscopy. Time-resolved and pressure dependent photoluminescence experiments show a ground optical transition of indirect type. Mixed k.p/tight-binding simulations indicate a possible indirect to direct crossover depending on indium content and QD size. The incorporation of nitrogen in QDs is finally shown.