Physics of strain effects in semiconductors and metal-oxide-semiconductor field-effect transistors

Abstract

A detailed theoretical picture is given for the physics of strain effects in bulk semiconductors and surface Si, Ge, and III–V channel metal-oxide-semiconductor field-effect transistors. For the technologically important in-plane biaxial and longitudinal uniaxial stress, changes in energy band splitting and warping, effective mass, and scattering are investigated by symmetry, tight-binding, and k⋅p methods. The results show both types of stress split the Si conduction band while only longitudinal uniaxial stress along ⟨110⟩ splits the Ge conduction band. The longitudinal uniaxial stress warps the conduction band in all semiconductors. The physics of the strain altered valence bands for Si, Ge, and III–V semiconductors are shown to be similar although the strain enhancement of hole mobility is largest for longitudinal uniaxial compression in ⟨110⟩ channel devices and channel materials with substantial differences between heavy and light hole masses such as Ge and GaAs. Furthermore, for all these materials, uniaxial is shown to offer advantages over biaxial stress: additive strain and confinement splitting, larger two dimensional in-plane density of states, smaller conductivity mass, and less band gap narrowing.

Measurement of effective electron mass in biaxial tensile strained silicon on insulator

“…Depending on the type of strain, electron and/or hole mobilities can be enhanced substantially, resulting in improved on-current, transconductance, etc., without geometrical scaling. 1 These enhancements are attributed either to strain-induced subband splitting, band warping, or reduced scattering.…”

Structural and band alignment properties of Al2O3 on epitaxial Ge grown on (100), (110), and (111)A GaAs substrates by molecular beam epitaxy

“…One enticing approach is to replace the Si channel with high intrinsic hole mobility Ge for p-channel device compared to III-V p-channel material. [8][9][10] Alternative approaches are different surface orientations to improve the carrier mobility, [11][12][13][14] strain engineering, 11,15,16 device architecture, 8,9,17 and optimal channel direction. [19][20][21][22][23] Research efforts are currently devoted towards investigation of the Ge as channel material, since higher intrinsic carrier mobility of Ge can provide a larger drive current, and its smaller bandgap can enable operation at a lower voltages.…”

Energy band alignment of atomic layer deposited HfO2 oxide film on epitaxial (100)Ge, (110)Ge, and (111)Ge layers

“…1 One attractive approach is to replace the Si channel with high intrinsic hole mobility Ge for p-channel and low effective carrier mass III-V material for n-channel material. [2][3][4][5] Alternative approach is different surface orientations to improve carrier mobility [6][7][8][9] and optimal channel direction for device speed. [10][11][12][13][14] Recently, semiconductor industry was replaced SiO 2 gate oxide by hafnium-based gate dielectric on Si complementary metal oxide semiconductor (CMOS) technology and demonstrated superior microprocessor performance compared to SiO 2 gate oxide.…”