Nanoscopic recombination processes in InGaN/GaN quantum wells emitting violet, blue, and green spectra

We investigated correlations between nanoscopic optical and structural properties in violet-emitting, blue-emitting, and green-emitting In(x)Ga(1-x)N/GaN quantum wells (QWs) by means of scanning near-field optical microscopy (SNOM) and atomic force microscopy. Only in the blue-emitting QW, threading dislocations were not major nonradiative recombination centers (NRCs). SNOM data indicated that NRCs in the blue-emitting QW are surrounded by energy levels higher than those for radiative recombination. Such potential distributions realize antilocalization of carriers to NRCs, which is the cause of high emission quantum efficiencies in blue emitters.