Formation of an absorbing layer and superfast gallium arsenide transition in the metal state under the action of femtosecond laser pulses

It has been shown experimentally that an electron-hole plasma forms in the surface layer at a depth of $\sim30$ nm, followed by a transition to the metallic state, when $\rm GaAs$ is exposed to femtosecond laser pulses with an intensity close to the melting threshold. This phenomenon is observed when laser pulses with photon energies are both smaller and larger than the band gap. The formation of an electron-hole plasma and an absorbing layer with metallic properties is mainly due to the mechanism of avalanche ionization by electron impact.