ABSORPTION OF LIGHT ASSISTED BY EQUILIBRIUM OPTICAL PHONONS IN GALLIUM ARSENIDE.

The influence of phonons on the long-wavelength wing of the fundamental absorption band of gallium arsenide was investigated experimentally. The absorption spectra were determined in the temperature range 4. 2-560 degree K. At temperatures T APP GRTH 200 degree K, a kink appeared in the wing. An analysis of the temperature dependence of the position of the kink and of the absorption coefficient in its vicinity indicated that the long-wavelength wing originated from the excitation of electron-hole pairs resulting from the simultaneous absorption of a photon and an optical phonon.