GaAs films were grown by metal organic chemical vapor deposition (MOCVD) on 400nm maskless round pillar patterned Si (100) substrate. The patterned substrate was fabricated by combining nanoimprint lithography with reactive iron etching. 1.8μm thick GaAs epilayer was obtained on the patterned substrate using two step method. The quality of GaAs was evaluated using etching pit density and transmission electron microscopy. The etching pit density of GaAs grown on patterned Si substrate at ~1×107cm-2 was two orders of magnitude lower compared with that grown on planar Si substrate. TEM observations reveal that most of the threading dislocations originated from the GaAs/Si interface were trapped near the top of the round pillars.
