One phonon absorption from aluminium complexes in silicon compensated by lithium or electron irradiation

• Published in: The Journal of physics and chemistry of solids 1970-01, Vol.31 (4), p.685-700
• Main Authors: Devine, S.D., Newman, R.C.
• Format: Article
• Language: English
• ISSN: 0022-3697; 1879-2553
• DOI: 10.1016/0022-3697(70)90202-7

Silicon containing 10 19 atom cm −3 of aluminium has been compensated by (a) lithium diffusion and (b) irradiation by 1.5 MeV electrons. The one phonon band mode absorption has been measured in both types of sample which contain Al −(s)-Li +(i) and Al −(s)-Al 2+(i) pair defects respectively; the latter centre has been identified by EPR measurements. In the lithium compensated sample in-band resonances were observed at 520 cm −1 due to Li and at 469 cm −1 and 431 cm −1 due to the paired Al −(s). A resonant mode at 242 cm −1 has been ascribed to the vibrations of Al 2+(i) in the irradiated sample and this is compared in detail with the similar lithium mode. This sample also showed marked absorption features characteristic of the critical point structure of the silicon density of states. These measurements are compared with neutron scattering data and previously measured one phonon absorption. The initial removal rate of Al −(s) by the irradiation as determined from resistivity measurements had the very high value of 2 atom per electron -cm. Interesting surface effects were also observed in these measurements and related to the diffusion of defects; the activation energy of diffusion of Al 2+(i) has been estimated to be about 1.2 eV. These results give further information about the products of the electron irradiation damage process, and also about the one phonon absorption associated with vacancy and interstitial impurity complexes.