Stress-induced alignment and reorientation of hydrogen-associated donors in silicon

Electron paramagnetic resonance (EPR) studies have been made of the stress- induced alignment and the subsequent recovery of the double donor (AA1 EPR center) that is formed in float-zone silicon following hydrogen implantatio n and annealing for similar to 20 min at a temperature above similar to 300 degrees C. The obtained data compare with those of the thermal double dono r (NL8 EPR center). The activation energy for atomic reorientation of the ( HDD+) AA1 defect is (2.3+/-0.1) eV. The reorientation rate is greater than that of the (TDD+) NL8 defect formed in Czochralski Si by a factor of 10(4) . Both centers have C-2 upsilon symmetry and piezospectroscopic measurement s reveal a large compressional strain along their [001] (three-axis) direct ion. However, in contrast to the NL8, the core of the AA1 defect produces a lso large compressional strain along its one-axis parallel to [110] directi on. These data demonstrate unambiguously that the two centers have differen t molecular structures, in spite of their similar EPR spectra and electrica l properties. It is suggested that the two centers have similar core struct ures (a [001]-oriented self-interstitials complexes), while the outer shell structure incorporates hydrogen pr oxygen atoms, respectively. (C) 1998 Am erican Institute of Physics. [S0021-8979(98)02721-2].