A study of oxygen atoms’ interactions on a GaAs (001) structure surface shows that these atoms are getting adsorbed onto the surface, form an oxide layer, and over time its thickness increases. This oxide layer hinders the injection of electrons and the holes from the metal layer to the semiconductor, thus affecting the photoelectroluminescence and the work of Metal-oxide-semiconductor diodes. These studies also examine the growth rate of oxide layers on the surface of the structure with different deposition degrees (400 ◦C, 630 ◦C) of cover layers and the extent of the oxygen atoms’ penetration into the structure.