Evidence for the Fourfold-Valley Confinement Electron Piezo-Effective-Mass Coefficient in Inversion Layers of < 110 > Uniaxial-Tensile-Strained (001) nMOSFETs

Abstract

We have recently experimentally extracted the piezo-effective-mass coefficients of 2-D electrons via the gate tunneling current of (001) n-channel metal-oxide-semiconductor field-effect transistors under < 110 > uniaxial compressive stress. The results pointed to the existence of a piezo-effective-mass coefficient around the fourfold conduction-band valley in the out-of-plane (quantum confinement) direction. To strengthen this further, here, we provide extra evidence. First, explicit guidelines are drawn to distinguish all the piezo-effective-mass coefficients. Then, a self-consistent strain quantum simulation is executed to fit literature data of both the mobility enhancement and gate current suppression in the uniaxial tensile stress situation. It is found that neglecting the fourfold-valley out-of-plane piezo-effective-mass coefficient, as in existing band structure calculations, only leads to a poor fitting.