Optical Absorption Edge in GaAs and Its Dependence on Electric Field

Abstract

Values of absorption constant covering the range 1 cm−1 to 104 cm−1 have been derived from transmission measurements made on single-crystal gallium arsenide. The absorption edge is very steep up to ∼4000 cm−1, where there is a knee beyond which the absorption increases relatively slowly with photon energy. The energy bands have been calculated using Kane's theory. From these a theoretical absorption curve has been obtained which shows very good agreement with the experimental data. Using semi-insulating material, it has been possible to measure the shift of the edge with applied electric field. The effect is small (∼200-μ ev shift for 5000-v/cm field) but is in good agreement with theory.