Electroreflectance of GaSe. II. 3.5–4.1 eV Region

Abstract

Electroreflectance spectra of ε-GaSe in the photon energy region 3.5–4.1 eV have been investigated at 77 K and at 300 K for F⁄⁄c with the Schottky-barrier technique and for F_⊥c with the transverse electroreflectance, where the light was incident nearly normal to the layers. It was found from the Kramers-Kronig analysis of the electroreflectance spectra at 77 K that the following five transitions exist whose transition energies, broadening energies in meV, and assignments, respectively, are those in the following parentheses: (3600±10, 40±5, M₁), (3700±5, \simeq20, excitonic M₀), (3860±10, 100±10, M₁^2D), (3895±10, 100±10, M₁^2D), and (4040±10, 50±10, M₁). The anisotropy of the reduced masses at the M₀ and M₁ critical points are found to be not so large as expected from the highly anisotropic crystal structure.