The optical absorption of molecular-beam-epitaxy-grown and Te-doped GaSb layers is measured in the spectral region of the fundamental absorption over a temperature range extending from 10 K to 300 K. In accordance with the Burstein-Moss description, a filling of the conduction-band states, resulting in a change of the shape and a shift of the absorption edge to higher energies, is observed in the absorption spectra of Te-doped n-type GaSb layers, with electron density ranging from 1.1 × 1016 to 7.6 × 1017 cm-3 at room temperature. A quantitative description of the Burstein-Moss effect is performed and the Fermi-level energy and the electron density in the Γ valley are obtained as a function of the temperature in two different ways: (i) by comparing absorption spectra of heavily doped and unintentionally or lightly doped GaSb samples; (ii) through a direct fit of absorption data performed in the framework of Kane's band model. The values of the Fermi level and of electron density in the Γ valley which have been optically obtained resulted in satisfactory agreement with those obtained from electrical measurements. The bandgap narrowing and the perturbation of the conduction-band density of states due to heavy doping in small-effective-mass semiconductors, such as GaSb, is considered in the framework of some current theoretical models.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics
- Electrical and Electronic Engineering
- Materials Chemistry