Excitation power dependent photoluminescence of In0.7Ga0.3As1−xNx quantum dots grown on GaAs (0 0 1)

The excitation power dependent photoluminescence (PL) of self-assembled In0.7Ga0.3As1−xNx (x=0,0.02) quantum dots (QDs) has been investigated in the excitation power density ranged from 3.0 kW/cm2 to 50 mW/cm2. As the excitation power increases, the emission peak of In0.7Ga0.3As0.98N0.02 QDs shifts to shorter wavelengths, while the peak of In0.7Ga0.3As QDs remains at the same wavelength. In the low-excitation cases, the PL peak of the In0.7Ga0.3As0.98N0.02 QDs has a tail on the lower energy side, on the other hand, that of the In0.7Ga0.3As QDs shows a symmetrical shape. Since the dot size distribution of the In0.7Ga0.3As0.98N0.02 QDs is similar to that of the In0.7Ga0.3As QDs, this blue-shift and the lower energy tail of the PL peak of the In0.7Ga0.3As0.98N0.02 QDs are attributed to the nitrogen-related states below the conduction band edge as are observed in the case of InGaAsN quantum wells (QWs).