High-Throughput Investigation of the Electron Transport Properties in Si₁-ₓGeₓAlloys

Bamidele Ibrahim Adetunji,Andrew Supka,Arrigo Calzolari,Marco Fornari

doi:10.1109/access.2021.3119898

Abstract

Si1– x Ge x alloys are among the most used materials for power electronics and quantum technology. In most engineering models the parameters used to simulate the material and its electronic transport properties are derived from experimental results using simple semiempirical approaches. In this paper, we present a high-throughput study of the electron transport properties in Si1– x Ge x alloys, based on the combination of atomistic first principles calculations and statistical analysis. Our results clarify the effects of the Ge concentration and of disorder on the properties of the Si1– x Ge x alloy. We discuss the results in comparison with existing semiempirical methods and we provide a Ge-dependent set of transport parameters that can be used in device modeling.

Highlights

After seminal works in the 70-80’s [1]–[3], Si1−x Gex alloys (SiGe) are attracting a renewed interest for the technological applications in the fields of power electronics [4] and quantum information [5]
Because of the low bandgap, the high carrier mobility, and the full compatibility with Si technology, SiGe is ideal for highend electronic devices [6] such as heterojunction bipolar transistors (HBT) [7], complementary metal oxide semiconductor (CMOS) with p-channel metal-oxide-semiconductorfield-effect-transistors (p-MOSFET) [8]–[10], fin field-effect transistors (FinFET) [11]–[13], and flash memories [14]
Most of existing density functional theory (DFT) studies focused on the low-doping regime, where Ge is assumed as a diluted impurity in the ideal Si crystalline host and whose effects can be described as a perturbation of the pristine system

Summary

INTRODUCTION

After seminal works in the 70-80’s [1]–[3], Si1−x Gex alloys (SiGe) are attracting a renewed interest for the technological applications in the fields of power electronics [4] and quantum information [5]. The most of existing works adopted semiempirical approaches for the electronic structure characterization (such as empiric pseudopotentials [25]–[27] tight-binding [28], [29] or k·p [30]–[32]) and Montecarlo methods [33], [34] for the electron transport characteristics In those cases, the effect of the Ge inclusion within the Si host is either parametrized from experimental data or deduced using the virtual crystal approximation (VCA) [35], [36]. We adopted a high-throughput approach that combines atomistic first principles calculations and statistical analysis This allows us to gain an unbiased characterization of the microscopic effects of Ge on the structural, electronic and transport properties of Si1−x Gex alloys. Our results support the validity of the semiempirical models used in the past and provide a Ge-dependent set of transport parameters (such conductivity, effective mass, Luttinger parameters) that can be used in device modeling

COMPUTATIONAL DETAILS

RESULTS AND DISCUSSION

CONCLUSION