Role of germanium nitride interfacial layers in HfO2/germanium nitride/germanium metal-insulator-semiconductor structures

The authors investigate the electrical properties of germanium nitride interfacial layers for germanium metal-insulator-semiconductor (Ge MIS) structures with HfO2 high-k dielectrics. A pure Ge nitride interfacial layer is fabricated by direct nitridation of a Ge substrate with the plasma processing before high-k deposition. The interface trap density of Au∕HfO2∕Ge niride/Ge MIS structures measured by the ac conductance method including the effect of the surface potential fluctuation is found to be as low as 1.8×1011cm−2eV−1 at the minimum. It is also found that Ge nitride interfacial layers mitigate the degradation of the accumulation capacitance during the high-temperature annealing.