Fig. 1. (a)–(c) Schematic structures of the InGaN QDs without capping, capped InGaN QDs, and InGaN QD LEDs.

Fig. 2. (a) X-ray reflectivity of QDs with and without capping; (b) omega-2theta scan curve of the QD LEDs.

Fig. 3. (a) AFM image of InGaN QDs; (b) height distribution of InGaN QDs extracted from the AFM image; (c) AFM image of QD LEDs; (d) TRPL measurements of capped QDs.

Fig. 4. (a) Cross-sectional TEM image of InGaN QDs sample with GaN capping layer; (b) high-magnification TEM image of the space between two neighboring QDs; (c) enlarged view of an InGaN QD; (d) STEM image of the interface between the InGaN QDs and GaN.

Fig. 5. TDPL spectra of (a) QD with capping and (b) QD LED; (c) PL peak energy; and (d) PL FWHM of InGaN QD with capping and QD LED.

Fig. 6. (a) Forward voltage versus injection current density; (b) LOP versus injection current density; (c) electroluminescence spectra of QD LED; (d) EQE as a function of current density.