Valence band properties of relaxed Ge1-xCx alloys
Journal
Materials Chemistry and Physics
Journal Volume
52
Journal Issue
1
Pages
31-35
Date Issued
1998
Author(s)
Abstract
We report hole effective mass calculations of Ge1-xCx alloys. A 16×16 Hamiltonian matrix constructed from the linear combination of atomic orbitals with spin-orbit interaction terms is used for the calculations. The properties of alloys are calculated under the virtual crystal approximation. The 1 meV constant energy surface below the valence band edge is used to determine the nominal hole effective masses. Calculations are carried out by taking the diamond split-off energy ΔEs-o(C) as 0 and 6 meV, respectively. In both cases, the light hole band results of Ge1-xCx alloys agree to within less than 1%. The effective masses of light hole increase monotonically from 0.078 m0 (for pure Ge) to 0.19 m0 (for pure C) while the non-parabolicity drops rather monotonically. The heavy hole effective masses of the alloys show a highly non-linear dependence on the carbon content (x). The results in both cases are indistinguishable from x=0.0 to about x=0.9; it decreases slightly from x=0.0 to x=0.5 and increases slowly fromx= 0.5 to x=0.9. The values increase for x>0.9. With ΔEs-o(C) =0 meV, there is an abrupt increase by a factor of two from x=0.97 to x=1.0 to a value of 0.89 m0. For ΔEs-o(C) =6 meV, a similar trend is found with a lower value of 0.45 m0 at x=1.0. The non-parabolicity of the heavy hole masses increases monotonically from x=0.0 to x=0.99, and nearly disappears for pure diamond for ΔEs-o(C) =0 meV, while a monotonic increase of non-parabolicity is found for ΔEs-o(C) =6 meV from pure Ge to pure C. The interaction between the split-off hole band and the heavy hole band is proposed for the anomalous behavior of the heavy hole effective masses of GeC alloys. © 1998 Elsevier Science S.A.
SDGs
Type
journal article