Molecular beam epitaxy of InGaN thin films on Si(111): Effect of substrate nitridation

The effect of silicon nitridation on structural quality, indium incorporation, and electrical properties of the InGaN/Si heterojunctions is investigated. A series of In_xGa_1 − xN (x = 0-0.32) thin films are grown directly on Si(111) substrates, with and without a Si_xN_y surface layer, by plasma-assisted molecular beam epitaxy. The crystalline quality is higher and the indium incorporation is increased when the In_xGa_1 − xN thin films are grown with the intentional Si_xN_y 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_xGa_1 − xN/p-Si (x = 0.2-0.3) heterojunctions exhibit a nearly ohmic behavior, and the series resistance is higher for the Si_xN_y-containing junctions. Our results suggest that unlike the amorphous Si_xN_y region spontaneously formed during direct deposition of III-nitrides on Si, the Si_xN_y layer obtained by high-temperature annealing of Si(111) in nitrogen atmosphere is beneficial to the In_xGa_1 − xN deposition.