Symmetry Breaking-induced Band-splitting in GaAs Thin Film by First-principles Calculations

Abstract

We investigated the band-splitting of GaAs thinˆlm by invoking broken inversion symmetry within the bulk region and the lost of 2D symmetry on the surface due to strain inˆrst-principles calculations using density functional theory with spin-orbit interaction. The system is modeled by unreconstructed GaAs(001)-(1×1) slab, and by its strained counterpart arising from As dimerization. For the unstrained system, we found that the valence bands split while the conduction bands remain degenerate. This degeneracy is attributed to the sole contribution of p-state of As atoms found on the surface to this band, where 2D symmetry is preserved. When strain is imposed on this surface, the symmetry is broken and the conduction bands are split. Thesê ndings identify the changes in the band structure due to broken symmetry, suggesting their incorporation in the conventional degenerate theoretical description of the GaAs thinˆlms done to date.

Terahertz generation in a thin GaAs slab in a tapered parallel plate waveguide by femtosecond laser excitation at 1560 nm

“…Unfortunately, highly stable, compact, and low-cost fiber lasers with a wavelength of 1560 nm have insufficient quantum energy for the above-band-gap excitation of LT-GaAs. Moreover, using two-step excitation via mid-gap states in LT-GaAs [9][10][11][12] as well as above-bandexcitation of narrow-band-gap InGaAs, 13,14) have not been reported to yield sufficient terahertz radiation efficiencies.…”