Energy distribution of interface traps in germanium metal-oxide-semiconductor field effect transistors with HfO_2 gate dielectric and its impact on mobility

摘要

The energy distribution of interface trap density (D_(it)) in HfO_2 gated germanium metal-oxide-semiconductor field effect transistors (MOSFETs) is investigated by using charge pumping method with variable rise/fall-time measurement. Our results reveal that a high density of interface traps is present in the upper half of the Ge bandgap. As a result, the inversion-layer electron mobility of Ge n-channel MOSFETs was significantly degraded by the Coulomb scatterings. These results are also consistent with the abnormal capacitance-voltage (C-V) characteristics of Ge MOS capacitors.