The effect of silicon nitridation on structural quality, indium, incorporation, and electrical properties of the InGaN/Si heterojunctions is investigated. A series of In(x)Ga(1-x)N (x = 0-0.32) thin films are grown directly on Si(111) substrates, with and without a Si(x)N(y) surface layer, by plasma-assisted molecular beam epitaxy. The crystalline quality is higher and the indium incorporation is increased when the In(x)Ga(1-x)N thin films are grown with the intentional SixNy buffer. These observations are explained by the reduced local elastic stress at the interface and N-polarity of the surface, both of which promote the incorporation of In. The obtained n-In(x)Ga(1-x)N/p-Si (x = 0.2-0.3) heterojunctions exhibit a nearly ohmic behavior, and the series resistance is higher for the Si(x)N(y)-containing junctions. Our results suggest that unlike the amorphous Si(x)N(y) region spontaneously formed during direct deposition of III-nitrides on Si, the Si(x)N(y) layer obtained by high-temperature annealing of Si(111) in nitrogen atmosphere is beneficial to the In(x)Ga(1-x)N deposition. (C) 2009 Elsevier B.V. All rights reserved.