Arrays of selectively grown GaN micro-pyramids: photonic and optical-frequency phonon properties

摘要

An array of GaN micro-pyramids containing a near-surface In_xGa_(1-x)N/GaN single quantum well has been fabricated using selective area epitaxial overgrowth above a patterned silica mask. The pyramid array has been studied by means of angle-resolved reflection measurements in the near- and mid- infrared optical ranges. We have found that the periodic array of flat-topped pyramids shows marked resonances in the near-infrared optical range due to resonant Bloch modes within the extraction cone and that the angular dispersion of these modes exhibits strong photonic crystal characteristics. The experimental results are in good agreement with the photonic band structure calculated using a scattering matrix formalism. The mid-infrared optical anisotropy properties of the micro-pyramids were investigated to probe the infrared active phonons of the pyramid array. The A_1(LO) phonon of the In_xGa_(1-x)N/GaN single quantum well was identified and the InN mole fraction was estimated from the mode behaviour.