Nanofabrication of InGaAsP periodic 2D columns with square and hexagonal lattices by reactive ion etching

Two-dimensionally arrayed nanocolumns were fabricated by using a double-exposure laser holography method. The hexagonal lattice was formed by rotating the sample with 60 deg while the square lattice by 90 deg before the second laser exposure. The size and period of nanocolumns could be controlled accurately from 80 to 150 nm in diameter and 220 to 450 nm in period for square lattice by changing the incident angle of laser beam. The reactive ion etching (RIE) for a typical time of 30 min using CH4/H2 plasma enhanced the aspect ratio by more than 1.5 with a slight increase of the bottom width of columns. Furthermore, it was observed that a wet etching after reactive ion etching enhanced the photoluminescence intensity of nanocolumns due to the removal of sidewall damage