Electron spin resonance study of point defects in thermal GaAs/GaAs-oxide structures

In an attempt to atomically assess interface and oxide-related point defects, a first basic multifrequency low-temperature electron spin resonance study has been carried out on semi-insulating (Fe compensated) GaAs/oxide structures, implying both powders and (100)GaAs/oxide slices, thermally grown in the range Tox=350–615 °C. Various spectra are observed: As for powders, this includes the 4-line EL2 defect spectrum centered at g∼2.043 and characterized by the isotropic hyperfine constant Aiso∼ 910 G, ascribed to the 75AsGa+ antisite defect. Observed in freshly crushed powder, it substantially increases in density with oxidation, in line with theoretical expectation; A maximum appears reached for at Tox∼440 °C. It is not observed in the parent c-GaAs wafer. A second isotropic signal is observed at g∼1.937 in powders for Tox in the range 510–615 °C, but only after additional VUV irradiation; it may correspond to As clusters. In bulk (100)GaAs, we observe the 5-branch spectrum of substitutional Fe impurities (spin S=5/2) in GaAs, with inferred crystal field constant a ≈ 360 G, well in line with previous observations. The results are discussed within the framework of advanced theoretical interface and defect models and previous experimental assessment.