Influence of Ultra-Thin Ge3N4 Passivation Layer on Structural, Interfacial, and Electrical Properties of HfO2/Ge Metal-Oxide Semiconductor Devices

We report the effects of the nitride passivation layer on the structural, electrical, and interfacial properties of Ge metal-oxide-semiconductor (MOS) devices with a hafnium oxide (HfO2) gate dielectric layer deposited on p-type (100) Ge substrates. X-ray photoelectron spectroscopy analysis confirmed the chemical states and formation of HfO2/Ge3N4 on Ge. The interfacial quality and thickness of the layers grown on Ge were confirmed by high-resolution transmission electron microscopy. In addition, the effects of post-deposition annealing (PDA) on the HfO2/Ge3N4/Ge and HfO2/Ge samples at 400 degrees C in an (FG + O-2) ambient atmosphere for 30 min were studied. After PDA, the HfO2/Ge3N4/Ge MOS device showed a higher dielectric constant (k) of similar to 21.48 and accumulation capacitance of 1.2 nF, smaller equivalent oxide thickness (EOT) of 1.2 nm, and lower interface trap density (D-it) of 4.9 x 10(11) cm(-2) eV(-1) and oxide charges (Q(eff)) of 7.8 x 10(12) cm(-2) than the non-annealed sample. The I-V analysis showed that the gate leakage current density of the HfO2/Ge3N4/Ge sample (0.3-1 nA cm(-2) at V-g = 1 V) was half of that of the HfO2/Ge sample. Moreover, the barrier heights of the samples were extracted from the Fowler-Nordheim plots. These results indicated that nitride passivation is crucial to improving the structural, interfacial, and electrical properties of Ge-based MOS devices.