Defect diffusion and aggregation in semiconductors.

Summary of EPSRC Grant GR/H91404
R Jones, School of Physics University of Exeter, EX4 4QL

The aims of the project were to extend a local density functional cluster technique (AIMPRO), developed at Exeter and Newcastle, to deal with the migration of defects and apply this to problems involving oxygen related defects and photoluminescent centres in silicon, and to various other defects of current interest such as residual donors in InP. The main achievements were:

1. The implementation of a method for determining migration energies.

2. The accurate calculation of the barrier to oxygen diffusion in Si and a description of the Y-lid saddle point structure.

3. The lowering of this barrier through the proximity of a second oxygen atom in the oxygen dimer, and possibly the trimer, which leads to an enhanced diffusion of these defects and an explanation for the rapid growth in thermal double donor defects.

4. The assignment of an N interstitial and a C-H interstitial to the cores of two shallow thermal donor species.

5. The elucidation of the structure and properties of the dominant nitrogen-oxygen defects.

6. The identification of a mechanism for converting deep level defects into shallow ones which might be used to design shallow donors in a wide range of materials.

7. A resolution of the problems related to the assignment of the 889 cm absorption line found in heat treated irradiated Si.

8. The successful collaboration with a) Kings College on the assignment of the T-photoluminescent centre in Si; b) the University of Paris on residual donors in InP; and c) with the University of Aarhus on the dominant nitrogen-oxygen complexes in Si.

9. A successful analysis of interstitial and substitutional carbon-oxygen defects, which has subsequently led to an assignment of a DLTS level to an interstitial defect.

10. The procurement, organisation and publication of the proceedings of a NATO advanced study workshop dealing with the early stages of oxygen precipitation in silicon.

Publications

Theoretical and Isotopic Infrared Absorption Investigations of Nitrogen-Oxygen Defects in Silicon, R. Jones, C. Ewels, J. Goss, J. Miro, P. Déak, S. Öberg, F. Berg Rasmussen, Semiconductor Science and Technology, 9, 2145-48 (1994).

The nitrogen-pair oxygen defect in silicon, F. Berg Rasmussen, S. Öberg, R. Jones, C. Ewels, J. Goss, J. Miro, and P. Déak, Materials Science and Engineering, B36, 91-5 (1996).

Vacancy and acceptor H complexes in InP, C. Ewels, S. Öberg, P. R. Briddon, J. Goss, R. Jones, and B. Pajot, Materials Science Forum, 196-201, 969-74, (1995).

Ab initio investigations of vacancy-oxygen defects in Si, C. Ewels, R. Jones, and S. Öberg, Materials Science Forum, 196-201, 1297-1302, (1995).

The NNO defect in Si, F. Berg Rasmussen, R. Jones, S. Öberg, C. Ewels, J. Goss, J. Miro, and P. Déak, Materials Science Forum, 196-201, 791-6, (1995)

Vacancy and Acceptor-H Complexes in InP, C. P. Ewels, S. Öberg, R. Jones, B. Pajot, and P. R. Briddon, Semicond, Sci. and Technol., 11, 502-7 (1996).

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

Shallow thermal donor defects in silicon, C. P. Ewels, R. Jones, S. Öberg, J. Miro, and P. Déak, International Conference on Shallow Donor Defects, Amsterdam, 1996.

Early Stages of Oxygen Precipitation in Silicon, ed. R. Jones, NATO ASI Series (3. High Technology) Vol. 17, Kluwer Academic Publishers, Dordrecht, 1996, pp 530.

Oxygen-carbon, oxygen-nitrogen and oxygen-dimer defects in silicon, C. P. Ewels, R. Jones, and S. Öberg, Early Stages of Oxygen Precipitation in Silicon, ed. R. Jones, NATO ASI Series (3. High Technology) Vol. 17, Kluwer Academic Publishers, Dordrecht, 1996, p 141.

Is Hydrogen A-B in hydrogenated GaAs:Mg? R. Bouanani-Rabi, B. Pajot, C. P. Ewels, S. Öberg, J. Goss, R. Jones, Y. Nissim, B. Theys, and C. Blauuw, International Conference on Shallow Donor Defects, Amsterdam, 1996.

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

Designing dopants in semiconductors: the conversion of deep level defects into shallow ones. R. Jones, and C. P. Ewels, submitted to Physics World.

Vibrational modes of oxygen complexes, in preparation, C. P. Ewels and R. Jones.