Exciton absorption of the GaAs semiconductor crystals under optical pumping to the conduction band

Modifications of the exciton structure of the fundamental absorption edge in the GaAs crystals is experimentally studied at $T$ = 1.7 K using the optical pumping at a photon energy that is significantly greater than the band gap. An increase in the amplitude of the fundamental state of the exciton is observed at a stable maximum energy. The dependence of the integral absorption on the pump intensity is interpreted in the framework of the concept of the excitonic polariton using the dissipative scattering of the exciton by free electrons that are generated by the pumping radiation. The constant of the electron-exciton interaction can be estimated with the aid of the solution to the inverse problem for initial pump levels. The integral absorption of the fundamental exciton state at liquid-helium temperatures can be used to characterize the purity of an epitaxial layer. The reasons for the lower saturation level of the integral absorption that is significantly less than the calculated level determined by the exciton oscillator strength need to be further studied.