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 (Φ_Bp) of 0.57 eV, resulting in a high junction current ratio of at the applied voltage |V_a| = ±1 V. The nMOSFET exhibited a high I_ON/I_OFF ratio of ~ 8×10³ (I_D), ~ 10⁵ (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.