Focused ion beam milled InGaN/GaN multiple quantum well nanopillars

The fabrication of nanopillars containing InGaN/GaN multiple quantum wells has been achieved via focused ion beam, using modified beam-shape tuning. Tuning the ion beam astigmatism and/or focusing permits control of the size and shape of Illnitride islands, which makes feasible the fast writing of large-area InGaN/GaN island arrays on epi-layer sample embedded with multiple quantum wells. Interestingly, some islands became high-aspect-ratio nanopillars intermittently under an adequate degree of defocus. Typically, the pillars have diameters of around 100-150 nm and heights of around 600-1500 nm. High-resolution cross-sectional transmission electron microscopy and Z-contrast imaging revealed the preserved perfection of single-crystalline nature and quantum well structure of one single pillar, respectively. The optical characterization on the pillars was also carried out by cathodoluminescence, and the peak position showed a blue shift of 35 meV compared with the original epi-layer wafer.