Hf O 2 high-κ gate dielectrics on Ge (100) by atomic oxygen beam deposition

Thin insulator films of the high-$\kappa$ dielectric $\mathrm{Hf}{\mathrm{O}}_2$ are deposited on Ge(100) substrates by evaporating Hf in atomic oxygen beams after in situ thermal desorption of the native oxide in ultrahigh vacuum and subsequent treatment of the clean Ge surface in oxygen and nitrogen. It is shown that $\mathrm{Hf}{\mathrm{O}}_2$ forms atomically sharp interfaces with Ge and behaves as an excellent insulator with dielectric permittivity $\kappa \sim 25$ , which is close to the expected bulk value. Very low equivalent oxide thickness of 0.75 (±0.1) nm with a low gate leakage current of $\sim 4.5\times {10}^{-4}\mathrm{A}∕{\mathrm{cm}}^2$ at 1 V in accumulation is achieved. Strong frequency dispersion of the inversion capacitance and low frequency behavior of the high frequency capacitance–voltage curves is observed. This is attributed to a combined effect of a high generation rate of minority carriers due to impurity traps and the high intrinsic carrier concentration in Ge, which result in a short minority carrier response time.