Space-charge behavior of ``Thin-MOS'' diodes with MBE-grown silicon films

We present basic theoretical and experimental characteristics of a novel "Thin-MOS" technology, which has promising aspects for integrated high-frequency devices up to several hundred gigahertz. The operation of such devices depends on charge injection into undoped silicon layers of ∼ 1000-Å thickness, grown by molecular beam epitaxy on heavily doped substrates, and isolation by thermally grown oxides of ∼ 100-Å thickness. Capacitance-voltage characteristics measured at "high" and "low" frequencies agree well with theoretical ones derived from uni- and ambipolar space-charge models. We conclude that after oxidation the residual doping in the epilayer is less than ∼ 10 ¹⁶ cm ^-3 and rises by 3 orders of magnitude at the substrate interface within less than 100 Å and that interface states at the oxide interface can be kept low.