Enhancing the Performance of Germanium Channel nMOSFET Using Phosphorus Dopant Segregation.

In this letter, we present a high performance Ge n-channel metal-oxide-semiconductor field-effect transistor (MOSFET) with a NiGe Schottky junction source/drain fabricated using phosphorus dopant segregation. Phosphorus atoms were implanted into NiGe and then driven toward the NiGe/p-Ge interface to depin the Fermi level and form a Schottky junction. A high effective barrier height (\PhiBp) of 0.57 eV, resulting in a high junction current ratio of >10^4 at the applied voltage \vertVa\vert=\pm1~V. The nMOSFET exhibited a high ION/IOFF ratio of \sim8\times 10^3~(ID), \sim10^5~(IS), and a subthreshold swing of 138 mV/decade. The nMOSFET developed in this letter exhibited greater transconductance and a drain leakage current that is more than two orders of magnitude lower compared with nMOSFETs with the conventional n^+/p junction. [ABSTRACT FROM AUTHOR]