InGaN nanorod arrays have been grown by molecular beam epitaxy on bare and high-temperature AIN-buffered Si(111) substrates. It has been found that well vertically aligned InGaN nanorod arrays can be grown by using the high-temperature AIN buffer layer. On bare Si substrate, high-resolution transmission electron microscopy revealed an amorphous SiNx layer generated at the interface, and the thickness and flatness of the SiNx layer may affect the relative alignment of the nanorods with the substrate. By using the high-temperature AIN buffer layer, the interface quality was improved, and uniform InGaN nanorods could be grown. N-InGaN nanorods/p-Si heterostructure diodes were fabricated, which exhibit well rectifying behavior with a low turn on voltage of 1.2 eV and an on/off ratio of 7.2 at 2.5 V.