Interface trap and border trap characterization for Al2O3/GeOx/Ge gate stacks and influence of these traps on mobility of Ge p-MOSFET

Interface traps (ITs) and border traps (BTs) in Al2O3/GeOx/p-Ge gate stacks were characterized using deep-level transient spectroscopy. Through evaluating the gate stacks with different GeOx thicknesses, the respective BTs in Al2O3, the Al2O3/GeOx interface region, and GeOx were detected. The density of ITs (D-it) near the midgap is lower in the metal-oxide-semiconductor (MOS) capacitors with thicker GeOx, while D-it near the valence band is lower in the MOS capacitor with thinner GeOx. The density of BTs (N-bt) in Al2O3 (6-9 x 10(17) cm(-3)) is lower than those in GeOx (similar to 2 x 10(18) cm(-3)), and the highest N-bt (similar to 1 x 10(19) cm(-3)) was found in the Al2O3/GeOx interface region. Ge p-channel metal-oxide-semiconductor field-effect-transistors (MOSFETs) with Al2O3/GeOx/p-Ge gate stacks were fabricated and analyzed. We confirmed that the ITs and the BTs near the valence band edge of Ge affect the effective mobility of Ge p-MOSFETs in the high-field region.