Effect of a Uniform Electric Field upon the Optical Absorption of Semi-Insulating Gallium Arsenide

The electric-field-induced effect upon the optical transmission of semi-insulating gallium arsenide has been measured for photon energies 1.4-2.0 eV. Electric fields up to 10⁵ V/cm were applied to samples ranging from 3.36 to 37 {μ} in thickness at both 25 and 90^∘{}K. In conjunction with zero-field optical-absorption-coefficient measurements, the effect of electric field upon optical-absorption coefficient has been measured. As the photon energy decreases below the experimentally observed edge (1.496 eV at 90^∘{}K, 1.503 eV at 25^∘{}K), the absorption falls almost exponentially. Above the edge, one or two large field-dependent oscillations are observed which correlate with the E2/3-dependent structure predicted separately by Callaway, by Tharmalingam, and more recently by Aspnes. Above 1.55 eV no conclusive evidence of a field-induced optical transmission effect was observed. At values of the electric field near 10⁵ V/cm, structure of an oscillatory nature was observed well below the absorption edge. The periodicity of the structure appears to be proportional to the applied electric field, but larger than the Wannier level structure predicted by Callaway.