Activation efficiency of C as p-type acceptor in GaAs and related compounds.

Summary of EPSRC Grant GR/K05528
R Jones, School of Physics University of Exeter, EX4 4QL

The aims of the project were to investigate a) the reasons for the low activation efficiency of carbon in GaAs, and b) to elucidate the properties of interstitial carbon defects in III-V semiconductors and Si. These aims were met through calculations carried out using the AIMPRO suite of code and our principal findings were:

1. The elucidation of the properties of an interstitial di-carbon centre in GaAs and AlAs which is stable, infra-red inactive and acts as a donor. These defects were subsequently discovered using Raman scattering studies carried out on annealed H-free material grown at Liverpool.

   This di-carbon centre largely accounts for the dramatic loss of over 90 in the hole concentration when GaAs:C is heat treated. Similar defects are also likely to account for the low activation efficiencies of other dopants in different materials, eg. N in ZnSe.

2. The elucidation of a mechanism for the enhanced dissociation of C-H complexes in GaAs in the presence of minority carriers.

3. The prediction of the low activation energy for the above process which has been subsequently confirmed by experimental work at NTT. These investigations demonstrate an inherent instability in certain devices fabricated using metallorganic doping sources.

4. The discovery of a strong tendency for C-Al ordering in Al doped GaAs, and a weak C-In binding in In doped GaAs, and that H will attack the defects creating C-Ga bonds in preference to C-Al bonds in the former Al doped material, and C-In bonds in the latter. These results are supported by IR investigations carried out at the IRC at London.

5. The determination of the properties of hydrogenated close-by pairs of carbon acceptors in GaAs and the prediction that both defects will lead to polarised absorption of IR radiation.

6. The resolution of the long standing problem posed by PL experiments carried out at King's College and elsewhere, concerning the bistable di-carbon centre C_i-C_s in Si, which conflicted with other experiments on these centres such as ODMR.

Publications

Interstitial hydrogen and the enhanced dissociation of C--H complexes in GaAs, S. J. Breuer, R. Jones, P. R. Briddon, S. Öberg, Phys. Rev. B, 53, 16289-96 (1996).

Mechanism for the enhanced dissociation of C-H complexes in GaAs, S. J. Breuer, R. Jones, P. R. Briddon, and S. Öberg, International Conference on Shallow Donor Defects, Amsterdam, 1996.

Di-carbon defects in annealed highly doped GaAs, J. Wagner, R. C. Newman, B. R. Davidson, S. P. Westwater, T. J. Bullough, T. B. Joyce, C. D. Latham, R. Jones, and S. Öberg, Physical Review Letters, 78, 74-7 (1997).

The Bonding of H-C_As Pairs in Al_xGa_1-x As Alloys, R. E. Pritchard, R. C. Newman, J. Wagner, F. Fuchs, K. H. Bachem, S. Öberg, R. Jones, A. Fischer, and K. Ploog, Phys. Rev. B, 50, 10628-36 (1994).

The bonding of C_As acceptors in In_x Ga_1-x As grown by chemical beam epitaxy using carbon tetrabromide as the source of carbon, M. J. Ashwin, R. E. Pritchard, R. C. Newman, T. B. Joyce, T. J. Bullough, J. Wagner, C. Jeynes, S. J. Breuer, R. Jones, P. R. Briddon, S. Öberg, J. Appl. Phys. 80, 6754-60 (1996).

(C_As)₂-Hydrogen Defects in GaAs - A First Principles Study, J. P. Goss, R. Jones, S. Öberg, and P. R. Briddon, Phys. Rev. B, submitted.

Peculiarities of interstitial carbon and di-carbon defects in Si, R. Jones, P. Leary, S. Öberg, and V. J. T. Torres. Materials Science Forum, 196-201, 785-790, (1995).

Dynamic Properties of Interstitial Carbon and Carbon-Carbon Pair Defects in Silicon, P. Leary, R. Jones, S. Öberg, V. J. B. Torres, Phys. Rev. B, in press.

Shallow Thermal Donor Defects in Silicon, C. P. Ewels, R. Jones, S. Öberg, J. Miro, P. Déak, Physical Review Letters, 77, 865-8 (1996).

Interstitial-Carbon Hydrogen Interaction in Silicon, A. N. Safonov, E. C. Lightowlers, Gordon Davies, P. Leary, R. Jones, S. Öberg, Physical Review Letters, 77, 4812-5, (1996).

The di-carbon hydrogen defect in silicon, A. N. Safonov, E. C. Lightowlers, G. Davies, A. Mainwood, P. Leary, R. Jones, and S. Öberg, Proceedings of the 23rd conference on the physics of semiconductors 1996, World Scientific, Singapore, New Jersey, London, ed M. Scheffler and R. Zimmermann, 2617-20.

Substitutional carbon in germanium, L. Hoffmann, J. C. Bach, B. Bech Nielsen, P. Leary, R. Jones, and S. Öberg, Phys. Rev. B, in press.

Light impurities in silicon, R. C. Newman, and R. Jones, Currrent Opinion in Solid State Materials Science in press.