Calculation of hole mobilities in relaxed and strained SiGe by Monte Carlo simulation

Abstract

Hole mobilities in relaxed and strained undoped SiGe layers have been calculated with a one-dimensional self-consistent bipolar Monte Carlo simulation code. We have adopted a novel bandstructure model that incorporates strain effects in the alloy valence band. Both alloying and strain enhance the hole mobility compared with bulk Si and we find that alloy scattering is the dominant scattering mechanism. An alloy potential of 1.4 eV was obtained by matching our Monte Carlo data on drift mobilities to experimental Hall mobility measurements. Uncertainties in this value arise from scatter in the experimental data and a lack of detailed knowledge of the Hall factor.

Atomistic approach to alloy scattering in Si1−xGex

“…Considerable effort has been spent on the realization of ultrathin strained SiGe channel devices 2,3 with alloy scattering being one of the major scattering mechanisms limiting the mobility. 4,5 Due to the lack of a consistent physical basis, ⌬U has been relegated to a mere fitting parameter. 6 The uncertainty in the definition and large discrepancy in the reported values of ⌬U has widely been discussed in literature.…”

Hall effect and ionized impurity scattering in Si(1−x)Gex

“…Experimental results for the Hall factor in relaxed SiGe have been reported by Chen et al 2 for impurity concentrations of about nϳ10 17 cm Ϫ3 ; and in SiGe strained to a Si substrate by Joelsson et al 1 for nϳ10 18 …”

Ensemble Monte Carlo Simulation of Hole Transport in SiGe Alloys

“…The dispersion relation of the valence band is required to evaluate the scattering rates of holes in SiGe alloys and the energy and the velocity of holes. A three-band approach is used to model the valence band of SiGe alloys [9], [10], [11]. This model considers the heavy-hole, the light-hole and the split-off bands.…”

“…This model considers the heavy-hole, the light-hole and the split-off bands. The dispersion relation of the split-off band is defined as spherical and parabolic [9], [12]. In this work, we calculated the split-off band of SiGe alloys employing the Empirical Pseudopotential Method (EPM) [13].…”