Electrical properties of atomic-beam deposited GeO1-xNx/HfO2 gate stacks on Ge

The electrical properties of GeO1-xNx/HfO2 stack deposited by atomic beam on Ge are reported. The incorporation of N in the GeOx layer was found to be quite beneficial in reducing the gate leakage current, improving the uniformity of the device characteristics, and reducing the equivalent oxide thickness of the gate stack down to similar to 0.8 nm. On the other hand, N incorporation also led to a large density of fixed positive charges and slow states, which can be reduced by post-deposition anneals in O-2 or N-2. These gate stacks were successfully integrated into a simple transistor flow with TiN gates. Both n- and p-channel transistors show promising electrical characteristics, with I-on/I-off ratios of about 4-5 orders of magnitude. However, the mobility of the n- channel devices was found to be extremely low, which is most likely related to a large density of acceptor-like interface states in the upper-part of the Ge bandgap. (c) 2006 The Electrochemical Society.