Formation of E4-centers (E c - 0.76 eV) in gallium arsenide

The paper deals with the effects of the bombarding-electron energy on the velocity of E4 center (E _c - 0.76 eV) formation and the temperature dependences of the efficiency of the latter in a neutral volume and the space-charge region of n-type gallium arsenide. The specimens were Schottky diodes manufactured by depositing titanium onto epitaxial layers of n-GaAs with n = (2-4)·10 ¹⁵ cm ³. The defect concentration was obtained by the DLTS spectroscopy method. It is shown that the number of E4 centers in the total amount of irradiation-induced defects sharply increases with increasing the bombarding-electron energy from 1.3 to 2.2 MeV. It is found out that the velocity of introducing E4 centers into the space-charge region does not depend on irradiation temperature and is by far higher than that in a neutral volume. In the latter, however, this velocity is non-linearly increasing with the irradiation temperature. It is assumed that an E4 center is a complex consisting of two unit defects generated in the adjacent sites of the Ga and As sublattices through a single collision. It is noted that its final configuration is formed as a result of interaction of these defects, which depends on the dynamics of transformation of their primary charge states.