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Lookup NU author(s): Professor Jon Goss,
Professor Patrick Briddon
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First principles calculations carried out on GaP containing sulfur donors (32)Sp (95%) and (34)Sp (5%) show that both the neutral and ionized donors are located on substitutional sites and have weak S-Ga bonds. For the sulfur impurity in its positive charge state the calculations give gap modes for S-32 and S-34 at frequencies close to those found experimentally. Modes within the gap are also predicted for neutral sulfur at frequencies within a few cm(-1) of their charged-state counterparts. However, the S-p(o) donor has a very low apparent charge (i.e. oscillator strength), its calculated integrated absorption cross section being only similar to 3 % of that for the S-p(+) defect. These results support an earlier explanation of the failure to detect gap modes from S-p(o) in infrared measurements. Calculated and observed apparent charges for the S-p(+) donor are compared, and the importance of taking due account of the different geometries that apply to the theoretical calculations and infrared experiments is emphasized.
Author(s): Leigh RS, Sangster MJL, Newman RC, Goss JP, Jones R, Torres VJB, Oberg S, Briddon PR
Publication type: Article
Publication status: Published
Journal: Physical Review B
ISSN (print): 1098-0121
ISSN (electronic): 1550-235X
Publisher: American Physical Society
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