Micro‐zone Optical Measurements on GaN Based Nitride/air Distributed Bragg Reflector (DBR) Mirrors Made by Focused Ion Beam Milling

Two kinds of three pairs nitride/air distributed Bragg reflector (DBR) with depth over 1.3 mum and vertical sidewall were successfully fabricated by focused Ga ion beam (FIB) milling. One was the combination of lst Bragg order air gap and 3rd Bragg order semiconductor wall DBR-A for the wavelength 514 nm, the other was the DBR-B facet with 3rd air gap and 5th semiconductor wall at 405 nm. To our best knowledge, the period of about 283 nm of these deep etched nitride/air DBR is the smallest one reported so far. Under a white light illumination, the DBR area shows special color at the expected wavelength. The properties of these DBR were investigated by the micro-zone measurements of reflectivity and photoluminescence (PL) respectively. As a result, the reflectivity of nitride/air DBR mirrors exhibited as high as 3.2-2.4 times of that of cleaved nitride facet and FIB etched facet at the concerned wavelength. The measured reflectivity data were compared with the calculation results from transfer matrix method and discussed. (C) 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.