Raman and photoluminescence characterization of focused ion beam patterned InGaN/GaN multi-quantum-wells nanopillar array

– XH Wang, JQ Ning, SJ Xu, and HW Choi

SEM images showing the nanopillar array at different stages of fabrication. (a) Immediately after FIB patterning. (b) Etched in acid to remove the ITO layer as well as the amorphous GaN layer due to ion bombardment, leaving a relatively smooth surface. (c) Further etched in KOH solution, shrinking the diameters of the nanopillars down to approximately 150 nm. (d) Fine milling of the array by FIB to form a small cluster of pillars.

Journal of Applied Physics, vol. 110, 9, pp. 093111 (2011)

High crystal quality GaN nanopillar arrays containing InGaN/GaN multi-quantum wells (MQWs) have been fabricated by focused ion beam followed by wet etch treatments to remove the ion damage. The first order Raman spectra reveal a well-built additional peak when the diameter of the nanopillars is less than 220 nm. This peak is also observed in the GaN pillars without MQW and is clearly assigned to the surface optical (SO) mode originating from the A1 phonon in wurtzite GaN. The frequency of this SO mode is found to be sensitive with the diameter and surface roughness of the nanopillars. Temperature-variable photoluminescence measurements show that a broadband emission in the as-grown sample split into the two well-resolved bands for nanopillars and the emission band at the higher energy side quickly thermally quenched.

DOI: 10.1063/1.3658866