Recently, we demonstrated that epitaxial and homogeneous wurtzite InN film on 4H-SiC substrate with a thickness down to 5 nm can be grown by using plasma ALD at 320°C, which has never been reported by other growth techniques. ALD thus seem to be more promising than other techniques to achieve homogeneous, epitaxial, nanometer-thin InN films. However, the understanding of why ALD hold such advantage over conventional thermal CVD is not properly addressed.