Electrical properties of Ge metal-oxide-semiconductor capacitors with La2O3 gate dielectric annealed in different ambient

Ge metal-oxide-semiconductor capacitors with La2O3 as gate dielectric are fabricated by e-beam evaporation of La2O3 followed by post-deposition annealing in different gases (NH3, N2, NO, N2O and O2). Experimental results indicate that the NH3, NO, N2O and O2 anneals give higher interface-state and oxide-charge densities, and thus larger gate leakage current, with the highest for the O2 anneal due to the growth of an unstable GeOx interlayer. On the other hand, the NH3 annealing improves the k value of the dielectric, while the annealings in O2-containing ambients (NO, N2O and O2) lead to the formation of a low-k GeOx interlayer, thus decreasing the equivalent k value. Compared with the above four samples, the sample annealed in N2 exhibits not only larger k value (18.3) and smaller capacitance equivalent thickness (2.14 nm), but also lower leakage current density (~ 10−3 Acm− 2 at Vg = 1 V) and smaller interface-state density (4.5 × 1011 eV− 1 cm− 2).