High-field optically detected EPR and ENDOR of semiconductor defects using W-band microwave Fabry–Pérot resonators

✍ Scribed by J.-M. Spaeth; I. Tkach; S. Greulich-Weber; H. Overhof

• Publisher: John Wiley and Sons
• Year: 2005
• Tongue: English
• Weight: 619 KB
• Volume: 43
• Category: Article
• ISSN: 0749-1581
• DOI: 10.1002/mrc.1663

✦ Synopsis

The designs of W-band (∼95 GHz) Fabry-Pérot microwave resonators for optically detected EPR and ENDOR using the magnetic circular dichroism of the optical absorption (MCDA) as well as for photo-luminescence-detected EPR are briefly described. We report on the first MCDA-detected high-field EPR/ENDOR investigation of the paramagnetic EL2 + defect in semi-insulating GaAs. The higher-order effects, which prevented the unambiguous analysis of previous MCDA-detected K-band EPR/ENDOR experiments could be suppressed in W-band. The analysis of the ENDOR spectra showed that an extremely precise alignment of the samples is necessary. The paramagnetic El2 + defect turned out to be an As antisite defect, which has four almost equivalent nearest 75 As neighbours differing less than 1.5% in the superhyperfine interactions suggestive of an isolated As antisite, while the third 75 As shell (fifth neighbour shell) is clearly of lower symmetry than expected for an isolated As antisite. We discuss as a possible solution to this paradoxical situation that EL2 + is an isolated antisite at room temperature, which at low temperature, where all magnetic resonance experiments are performed, associates itself with shallow acceptors such as Zn Ga -more than two nearest neighbour distances away. According to recent theoretical calculations, such 'loose' complexes with binding energies between 0.01 eV and 0.05 eV and disturb the equivalence of the nearest neighbour superhyperfine (shf) interactions less than 1.5%. Also, W-band EPR was measured using the photo-luminescence for detection to investigate P dopants in 6H-SiC.