GaN quantum dots in (Al,Ga)N-based Microdisks

We report on the fabrication and study of (Al,Ga)N microdisks with embedded GaN quantum dots. In order to facilitate the microdisk fabrication, very thin (h < 120 nm) nitride epilayers containing optically efficient GaN quantum dots are grown directly on silicon substrates. The microdisks defined by optical lithography exhibit whispering-gallery modes with a short 1.2 nm mode spacing and quality factors as high as 2000. We show that the quality factor is limited by scattering losses due to the microdisk sidewall roughness. Finally, using e-beam lithography, we obtain microdisks with enhanced features.