Expansion of the Electron‐Hole Liquid Plasma at GaAs Surface

The spectral and planar distribution of the luminescence intensity of the electron‐hole plasma (EHP) created by laser excitation in the subsurface region of a direct‐band semiconductor like GaAs in contact with a dielectric medium (Si 3 N 4 ) is studied. High optical excitation levels ( L ≈ ≈ 5 MW/cm 2 ) make possible to detect: (1) the appearance of stimulated radiation mainly from the regions of the sample edges; (2) the expansion of EHP from the excited region predominantly along the GaAs‐Si 3 N 4 interface up to a distance ( l ≈ 50 to 100 μm), which is several times greater than the corresponding bulk value. The assumption is made that the electron‐hole liquid is created not only at the “tails” of the expanded plasma, but also within the excited regions (in the latter case after a partial cooling of EHP, when in the process of the relaxation the electron‐hole pairs concentration achieves the EHP‐condensation value n ≈ 10 16 cm −3 ). The mechanism of a long‐wave range tail formation in EHL radiation, which is caused by the energy losses on non‐equilibrium plasmons, is discussed.