Submicro-electroluminescence spectroscopy of dodecagonal micropit-arranged blue light-emitting diodes

We investigate the local electroluminescence (EL) characteristics of c-plane blue InGaN/GaN light-emitting diodes (LEDs) with periodically arranged dodecagonal micropits (DMs) which have {10-1-1} and {11-2-2} facets using confocal scanning electroluminescence microscopy (CSEM). By increasing the injection current from 1 to 20mA, the EL peak for c-plane LEDs is shifted to a shorter wavelength (by up to 5.5nm), but the EL peaks for semi-polar {10-1-1} and {11-2-2} facets are nearly unchanged because of the substantially reduced polarization-related electric fields in the quantum wells. CSEM images show various emitting distributions due to the different emission origins as a function of peak position in the EL spectrum. The present observations can help one to improve the understanding of the spatial origin of increased external quantum efficiency in InGaN LEDs with DM arrays.