Band offset predictions for strained group IV alloys: Si_1-x-yGe_xC_yon Si(001) and Si_1-xGe_xon Si_1-zGe_z(001)

Abstract

The band offsets for strained Si 1−x−y Ge x C y layers grown on Si(001) substrate and for strained Si 1−x Ge x layers grown on fully relaxed Si 1−z Ge z virtual substrates are estimated. The hydrostatic strain, the uniaxial strain and the intrinsic chemical effect of Ge and C are considered separately. Unknown material parameters relative to the latter effect are chosen to give the best agreement with the available experimental results for Si 1−x Ge x and Si 1−y C y layers on Si. As a general trend concerning carrier confinement opportunities, it is found that a compressive strain is required to obtain a sizeable valence band offset, while a tensile strain is needed to obtain a conduction band discontinuity. In most cases the strain is responsible for a bandgap narrowing with respect to that of the substrate. The obtained results are in very good agreement with available experimental determinations of band offsets and bandgap changes for ternary alloys on Si(001).

Fabrication technology of SiGe hetero-structures and their properties

“…Therefore, process margin for SiGe HBT fabrication can be relaxed. On the other hand, it has been reported that the bandgap and the band offsets with respect to the conduction band and valence band sensitively varies with C contents and strain in Si 1ÀxÀy Ge x C y films [151][152][153][154][155][156][157][158][159][160][161]. On the basis of the control over the band alignment in the Si 1ÀxÀy Ge x C y hetero structures, Si 1ÀxÀy Ge x C y epitaxial films were applied to channel layers in MOSFET [162,163], high-electron mobility transistor (HEMT), and optical devices [164][165][166].…”

Electron transport in Si/SiGe modulation-doped heterostructures using Monte Carlo simulation

“…This type of biaxial strain introduces a splitting of degenerate bands [1][2] which results, for both electrons and holes, in smaller in-plane effective mass and reduced intervalley scattering yielding improved transport properties. N-type Si/SiGe modulation-doped FETs (MODFETs) have demonstrated low noise figure and high cut-off and maximum oscillation frequencies [3][4].…”

On the reduction of direct tunneling leakage through ultrathin gate oxides by a one-dimensional Schrödinger–Poisson solver

“…A coherent strain applied along direction ͑001͒ lifts at least partially the degeneracy of conduction and valence bands. 35 In case of tensile strain the energy position of normal ⌬ valleys shifts down, whereas that of parallel valleys shifts up, as illustrated in Fig. 6.…”

“…33,34 A similar design of n-type MOSFET requires a tensile strained layer to create a convenient conduction band offset. 35 Two types of heterostructures may be used in this order. Classically, a tensile strain is obtained by growing a Si layer on a Si 1Ϫx Ge x virtual substrate.…”