HfO2 high-κ gate dielectrics on Ge(100) by atomic oxygen beam deposition -: art. no. 032908

Thin insulator films of the high-kappa dielectric HfO2 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 HfO2 forms atomically sharp interfaces with Ge and behaves as an excellent insulator with dielectric permittivity kappasimilar to25, 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 similar to4.5x10(-4) A/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. (C) 2005 American Institute of Physics.