For the first time, we attempted to grow maskless selective epitaxial films of InGaN and obtained cubic InGaN on GaAs (1 0 0) and hexagonal InGaN on GaAs (1 1 1) A and (1 1 1) B substrates by using an Inca low energy focused ion beam and dimethylhydrazine as III and V sources, respectively. These results are in good agreement with those grown by MBE or MOCVD method. From these results, this growth method is thought to be very useful in fabricating microstructures on selective areas without mask.