Theory of hole mobility in strained Ge and III-V p-channel inversion layers with high-kappa insulators

We present a comprehensive investigation of the low-field hole mobility in strained Ge and III-V (GaAs, GaSb, InSb, and In(1-x)Ga(x)As) p-channel inversion layers with both SiO(2) and high-kappa insulators. The valence (sub) band structure of Ge and III-V channels, relaxed and under biaxial strain (tensile and compressive) is calculated using an efficient self-consistent method based on the six-band k.p perturbation theory. The hole mobility is then computed using the Kubo-Greenwood formalism accounting for nonpolar hole-phonon scattering (acoustic and optical), surface roughness scattering, polar phonon scattering (III-Vs only), alloy scattering (alloys only) and remote phonon scattering, accounting for multisubband dielectric screening. As expected, we find that Ge and III-V semiconductors exhibit a mobility significantly larger than the "universal" Si mobility. This is true for MOS systems with either SiO(2) or high-kappa insulators, although the latter ones are found to degrade the hole mobility compared to SiO(2) due to scattering with interfacial optical phonons. In addition, III-Vs are more sensitive to the interfacial optical phonons than Ge due to the existence of the substrate polar phonons. Strain-especially biaxial tensile stress for Ge and biaxial compressive stress for III-Vs (except for GaAs) - is found to have a significant beneficial effect with both SiO(2) and HfO(2). Among strained p-channels, InSb exhibits the largest mobility enhancement. In(0.7)Ga(0.3)As also exhibits an increased hole mobility compared to Si, although the enhancement is not as large. Finally, our theoretical results are favorably compared with available experimental data for a relaxed Ge p-channel with a HfO(2) insulator. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3524569

Calculation of the electron mobility in III-V inversion layers with high-kappa dielectrics

We calculate the electron mobility for a metal-oxide-semiconductor system with a metallic gate, high-kappa dielectric layer, and III-V substrate, including scattering with longitudinal-optical (LO) polar-phonons of the III-V substrate and with the interfacial excitations resulting from the coupling of insulator and substrate optical modes among themselves and with substrate plasmons. In treating scattering with the substrate LO-modes, multisubband dynamic screening is included and compared to the dielectric screening in the static limit and with the commonly used screening model obtained by defining an effective screening wave vector. The electron mobility components limited by substrate LO phonons and interfacial modes are calculated for In0.53Ga0.47As and GaAs substrates with SiO2 and HfO2 gate dielectrics. The mobility components limited by the LO-modes and interfacial phonons are also investigated as a function of temperature. Scattering with surface roughness, fixed interface charge, and nonpolar-phonons is also included to judge the relative impact of each scattering mechanism in the total mobility for In0.53Ga0.47As with HfO2 gate dielectric. We show that InGaAs is affected by interfacial-phonon scattering to an extent larger than Si, lowering the expected performance, but probably not enough to question the technological relevance of InGaAs. (C) 2010 American Institute of Physics. [doi:10.1063/1.3500553

Spintronic Majority Gates

In this paper we present an overview of two types of majority gate devices based on spintronic phenomena. We compare the spin torque majority gate and the spin wave majority gate and describe work on these devices. We discuss operating conditions for the two device concepts, circuit implication and how these reflect on materials choices for device implementation