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In this paper we present a reliable process to fabricate GaN/AlGaN onedimensional photonic crystal (1D-PhC) microcavities with nonlinear opticalproperties. We used a heterostructure with a GaN layer embedded between twoDistributed Bragg Reflectors consisting of AlGaN/GaN multilayers, on sapphiresubstrate, designed to generate a {\lambda}= 800 nm frequency down-convertedsignal (\chi^(2) effect) from an incident pump signal at {\lambda}= 400 nm. Theheterostructure was epitaxially grown by metal organic chemical vapourdeposition (MOCVD) and integrates a properly designed 1D-PhC grating, whichamplifies the signal by exploiting the double effect of cavity resonance andnon linear GaN enhancement. The integrated 1D-PhC microcavity was fabricatecombing a high resolution e-beam writing with a deep etching technique. For thepattern transfer we used ~ 170 nm layer Cr metal etch mask obtained by means ofhigh quality lift-off technique based on the use of bi-layer resist (PMMA/MMA).At the same time, plasma conditions have been optimized in order to achievedeeply etched structures (depth over 1 micron) with a good verticality of thesidewalls (very close to 90{\deg}). Gratings with well controlled sizes(periods of 150 nm, 230 nm and 400 nm respectively) were achieved after thepattern is transferred to the GaN/AlGaN heterostructure.

Fabrication of GaN/AlGaN 1D photonic crystals designed for nonlinear optical applications