Optical dielectric functions of wurtzite III-V semiconductors

Optical properties of semiconductors can exhibit strong polarization dependence due to crystalline anisotropy. A number of recent experiments has shown that the photoluminescence intensity in free standing nanowires is polarization dependent. One contribution to this effect is the anisotropy of the dielectric function due to the fact that most nanowires crystalize in the wurtzite form. While little is known experimentally about the band structures of wurtzite phase III-V semiconductors, we have previously predicted the bulk band structure of nine III-V semiconductors in the wurtzite phase. Here, we predict the frequency dependent dielectric functions for nine non-nitride wurtzite phase III-V semiconductors (AlP, AlAs, AlSb, GaP, GaAs, GaSb, InP, InAs, and InSb). Their complex dielectric functions are calculated in the dipole approximation for light polarized parallel and perpendicular to the c axis of the crystal. Momentum matrix elements are evaluated on a dense grid of special k points using empirical pseudopotential wave functions. Corrections to the momentum matrix elements, to account for the missing core states, are made using a scaling factor which is determined from the zinc-blende polytypes. Simple analytic expressions are provided for the dispersion relations in the vicinity of the respective fundamental absorption edges.