Influence of the free-electron concentration on the optical properties of zincblende GaN up to 1 ×1020cm-3
Abstract
We analyze the optical properties of zincblende gallium-nitride in the infrared and ultraviolet spectral range (≈27 meV -6.5 eV ) experimentally by spectroscopic ellipsometry and provide a quantitative description of these results by k .p perturbation theory. Free-electron concentrations above 1020cm-3 are achieved by introducing germanium as a donor. We determine the dielectric function as well as band filling effects like the Burstein-Moss shift and band gap renormalization. The Kane model for the band structure of semiconductors near the Γ -point allows to calculate the effective electron mass and to determine the nonparabolicity of the conduction band. At the same time, these results can be used to derive the free-electron concentration all-optically. The combination of Kane's model, Burstein-Moss shift, and band-gap renormalization can be used to expertly describe the measured transition energies up to ≈3.7 eV dependent on the carrier concentration, yielding an averaged hole mass of ≈0.61 me for the contributing valence bands.
- Publication:
-
Physical Review Materials
- Pub Date:
- October 2019
- DOI:
- 10.1103/PhysRevMaterials.3.104603
- Bibcode:
- 2019PhRvM...3j4603B