Conduction-band dispersion relation and electron effective mass in III-V and II-VI zinc-blende semiconductors

Adjusting calculated spectra of the imaginary part epsilon(2) of the dielectric function to experimental ones in a spectral region close to and above the fundamental absorption edge, we determined the conduction-band dispersion relation for 12 III-V and II-VI semiconductors with zinc-blende crystal structure and deduced the corresponding nonparabolicity coefficients. This yields an experimental determination of the conduction-band nonparabolicity and momentum electron effective mass as a function of the wave vector and free electron concentration. For most of the semiconductors, we present experimental data extended to electron energies between 0.6 and 2.2 eV, which are significantly higher than those achievable by doping or in magnetic fields. In addition, examination of experimental dielectric functions reported by various authors showed that the magnitude of epsilon(2) is overestimated in the existing literature data for GaSb, ZnTe, ZnS, and CdSe, probably due to the neglect or incorrect treatment of possible overlayers.