Deep-level transient spectroscopy study of electron traps in rapid thermally annealed SiO₂-capped n-type GaAs layers grown by metalorganic chemical vapour deposition

Three dominant electron traps S1 (E_c - 0.23 eV), S2* (E_c - 0.53 eV), and S4 (E_c - 0.74 eV) are introduced in SiO₂/n-GaAs after rapid thermal annealing (RTA). A defect S3 (E_c - 0.72 eV) is observed in uncapped and annealed samples only. The S2* arises from the superposition of two defects, of which S2 (E_c - 0.46eV) can be resolved using filling pulse widths <1 ms. The intensities of S1, S2*, and S4 show Arrhenius-like dependencies on the RTA temperature. We argue that the defects are formed as a result of an increase in the ratio of As:Ga in the near-surface region of the GaAs layers. The electronic and annealing properties of S4 show that it is a member of the EL2 family of defects. The removal of S1 and S2*, as well as the introduction of secondary defects, during isochronal annealing experiments is also discussed.