Enhancing the Performance of Germanium Channel nMOSFET Using Phosphorus Dopant Segregation

Abstract

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 (Phi(Bp)) of 0.57 eV, resulting in a high junction current ratio of >10(4) at the applied voltage vertical bar V-a vertical bar = +/- 1 V. The nMOSFET exhibited a high I-ON/I-OFF ratio of similar to 8 x 10(3) (I-D), similar to 10(5) (I-S), 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.