Abstract
Direct gap Ge1−xSnx alloys under [100] and [110] uniaxial strain are comprehensively investigated by theoretical calculations using the nonlocal empirical pseudopotential method (EPM). It is shown that [100] uniaxial tensile strain aids indirect-to-direct gap transition in Ge1−xSnx alloys. The Γ electron effective mass along the optimal direction under [110] uniaxial strain is smaller than those under [100] uniaxial strain and (001) biaxial strain. Additionally, the direct tunneling gap is smallest along the strain-perpendicular direction under [110] uniaxial tensile strain, resulting in a maximum direct band-to-band tunneling generation rate. An optimal [110] uniaxial tensile strain is favorable for high-performance direct gap Ge1−xSnx electronic devices.
Highlights
Germanium-tin (Ge1−xSnx) alloys have attracted a great deal of research attention
The small band gaps and direct gap properties of Ge1−xSnx alloys are beneficial for enhancing the band-to-band tunneling (BTBT) rate, which is critical for improving the on-state current of tunneling FETs (TFETs) in practical applications
The virtual crystal approximation (VCA) can be used to describe the semiconductor alloys within the empirical pseudopotential method (EPM) framework, and the corresponding pseudopotentials and parameters are linearly interpolated in this scheme
Summary
Germanium-tin (Ge1−xSnx) alloys have attracted a great deal of research attention. The electronic band structures of Ge1−xSnx alloys are strongly dependent on their Sn composition x.1–4. Incorporating more Sn atoms into Ge1−xSnx alloys would result in a transition from an indirect gap to a direct gap, making it possible to achieve direct gap semiconductors with Group IV elements.. Direct gap Ge1−xSnx alloys are very promising materials for optoelectronic applications.. Ge1−xSnx alloys are expected to exhibit enhanced carrier transport capability, which would allow them to be used as high mobility channel materials for the generation of metal-oxide-semiconductor field-effect transistors (MOSFETs).. The small band gaps and direct gap properties of Ge1−xSnx alloys are beneficial for enhancing the band-to-band tunneling (BTBT) rate, which is critical for improving the on-state current of TFETs in practical applications.. Direct gap Ge1−xSnx alloys are of great importance for novel high-performance electronic devices. Theoretical calculations and experimental results of the direct gap transition compositions of
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