Diverse facets of InGaN quantum well microrings grown by selective area epitaxy

InGaN quantum well (QW) microrings were grown using selective area epitaxy on patterned (0001) AlN/sapphire. The well defined shapes are comprised of {112¯2} and {213¯3} facets on inner sidewalls, and {11¯01} facets on outer sidewalls, as well as (0001) top surfaces. The sidewall facets exhibit distinct emission spectra when investigated using cathodoluminescence. Differences in emission spectra are attributed to variations in growth rate and indium incorporation on the facets, with peak emission wavelength as long as 500 nm. The observed weak blueshift with increasing cathodoluminescence excitation current verifies that the internal piezoelectric fields of the semipolar sidewall facets are lower than reference (0001) InGaN QWs.