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

Abstract

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 ( $\Phi _{{{\textrm {Bn}}}})$ of 0.59 eV, resulting in a high junction current ratio of more than $10^{5}$ 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 ( $L = 4~\mu \text{m}$ ) exhibited high $I_{{\mathrm{\scriptscriptstyle ON}}}/I_{{\mathrm{\scriptscriptstyle OFF}}}$ ratios of approximately $3.7 \times 10^{3}$ ( $I_{D})$ and $1.3 \times 10^{5}$ ( $I_{S})$ and a moderate subthreshold swing of 126 mV/dec.