Channel direction, effective field, and temperature dependencies of hole mobility in (110)-oriented Ge-on-insulator p-channel metal-oxide-semiconductor field-effect transistors fabricated by Ge condensation technique

Abstract

This paper experimentally reports the channel direction (θ), effective field (Eeff), and temperature (T) dependencies of hole mobility in (110)-oriented 12-nm-thick accumulation mode Ge-on-insulator (GOI) p-channel metal-oxide-semiconductor field-effect transistors (pMOSFETs) fabricated by the Ge condensation technique. It is found that, the hole mobility on (110)-oriented GOI surfaces increases with the channel direction tilted from ⟨100⟩ to ⟨110⟩ direction, in contrast to (100)-oriented conventional GOI surfaces. By low temperature measurements, the extracted phonon-limited mobilities (μph) of (110)-oriented GOI surfaces along ⟨110⟩ direction occupy 2.1 and 7.1 of enhancement against (100)-oriented GOI and Si surfaces, respectively, at any T. Through physical insights into the present analyses, μph dependence on T−1.8 suggests the suppression of intervalley phonon scattering at low T as in Si. Also, μph is found to increase with Eeff, which can be regarded as an inherent property of hole mobility on (110)-oriented Ge. By further analyses base on the definition of mobility, the effective mass can be a dominant factor for the mobility anisotropy on (110)-oriented GOI pMOSFETs.