Experimental Realization of a Ternary-Phase Alloy Through Microwave-Activated Annealing for Ge Schottky pMOSFETs

This paper presents a high-performance Ge p-channel MOSFET (pMOSFET) with NiGePt as a ternary-phase alloy of Schottky source/drain (S/D) formed through low-temperature microwave-activated annealing (MWA). We fabricated a NiGePt alloy contact with uniform crystallinity through structural engineering and MWA. We clarified the phenomena of thermal reaction and diffusion for forming ternary-phase alloys using MWA properties such as thermal dynamics and ionic transportation. The ternary-phase NiGePt alloy is crucial for improving the off-leakage current of the junction. A lower process temperature is beneficial for eliminating surface roughness and reducing alloy agglomeration of the Schottky contact S/D. Consequently, the fabricated NiGePt/n-Ge Schottky junction exhibited a high effective barrier height (Φ_Bn) of 0.59 eV, resulting in a high junction current ratio of more than 10⁵ at an applied voltage of /V_a/ = 1 V. In addition, we exploited the advantages of low-temperature microwave annealing to fabricate the pMOSFET, which includes a GeO₂ passivation layer and a Schottky S/D. Our ternary Schottky Ge pMOSFET ( L = 4 μm) exhibited high I_ONI_OFF ratios of approximately 3.7 × 10³ (I_D) and 1.3 × 10⁵ (I_S) and a moderate subthreshold swing of 126 mV/dec.