Gating of germanium surfaces using pseudomorphic silicon interlayers

A novel insulator structure for gating of germanium surfaces has been developed. The structure consists of a very thin (on the order of 10 Å) pseudomorphic silicon layer deposited on the germanium surface prior to deposition of a silicon dioxide insulating layer. Both the silicon and silicon dioxide layers were deposited at low temperature by remote plasma-enhanced chemical vapor deposition. Low interface state densities and surface inversion have been obtained for both n- and p-type germanium substrates. X-ray photoelectron spectroscopy and ion scattering spectroscopy analysis indicate that the thin pseudomorphic silicon layer provides complete silicon coverage of the germanium surface. The silicon layer protects the germanium surface from undesirable oxidation during the silicon dioxide deposition. The electrical properties of germanium metal-insulator-semiconductor structures which incorporated the silicon interlayer were much improved compared to structures in which the silicon dioxide was deposited directly on the germanium.