Diamond and Related Materials 13 (2004) 684–690 0925-9635/04/$ - see front matter  2003 Elsevier B.V. All rights reserved. doi:10.1016/j.diamond.2003.08.028 Donor and acceptor states in diamond J.P. Goss *, P.R. Briddon , R. Jones , S. Sque a, a b b School of Natural Sciences, Herschel Building, University of Newcastle upon Tyne, Newcastle NE1 7RU, UK a School of Physics, University of Exeter, Exeter EX4 4QL, UK b Abstract We present the results of density functional calculations of donor and acceptor characteristics of defects in diamond. We compare different computational approaches and relate the calculations to experimental data where available. We find that the best method appears to be comparing levels of the defects with some known reference state. Furthermore, a number of pnictogen and chalcogen–hydrogen defects have shallow donor qualities, and we comment on the electrical levels of boron–hydrogen complexes potentially present in p-type CVD diamond.  2003 Elsevier B.V. All rights reserved. Keywords: Electrical properties characterisation; Band structure; n-Type doping 1. Introduction Although donor and acceptor levels (labelled (0yq) and (yy0)) of point defects in a range of materials such as silicon, germanium and III–V materials have been extensively studied using theoretical and experi- mental methods, the situation is somewhat different for diamond. The importance of defects as deep traps for carriers or as non-radiative recombination centres is becoming significant now that diamond is becoming a viable electronic material w1x. For narrow-gap semi-conductor materials the electri- cal levels describe an ability to trap free carriers, and in equilibrium and zero-bias indicate the charge state that a defect will adopt given the Fermi-level in the material. However, for diamond (an insulator) the concept of a Fermi-level is perhaps less relevant, and it has been suggested that the proximity of defects to dopants is crucial w2x. However, for inhomogeneous, e.g. polycrys- talline samples, where some impurities favour one growth sector over others, the Fermi-level has to be interpreted with great care. In a small number of instances the electrical levels of impurities and lattice defects have been obtained exper- imentally, predominantly for impurities such as substi- *Corresponding author. Tel.: q44-191-222-7425; fax: q44-191- 222-7631. E-mail address: j.p.goss@ncl.ac.uk (J.P. Goss). tutional N, P and B and to a lesser extent N-complexes and other optically and magnetically active centres. The defects present in the samples depend on the history of the material and in particular whether it is natural or synthetic. CVD diamond commonly contains isolated impurity defects including nitrogen, silicon and boron, and it has recently become clear that hydrogen plays a role in the formation of electrically active defects. High- temperature–high-pressure synthetic diamonds may con- tain isolated substitutional nitrogen if getters have not been employed, and, where Ni is present in as part of the solvent-catalyst, a range of Ni-related defects have also been found, many of which are apparently electri- cally active. Natural diamonds most commonly have N present in aggregated forms, and some rare samples contain boron and are semiconducting. The future use of diamond as an electronic material, even in the most simple devices such as p–i or pn junctions, is in many ways dependent on the ability to passivate or remove compensating electrically active defects. Furthermore, despite the fabrication of n-type material, the donor level of P is relatively deep and renders room temperature operation difficult. There is, therefore, a dual role for high-quality quan- tum-mechanical simulation techniques. On one side, there is the predictive calculation of potential compen- sation centres or shallow dopants, and on the other, there is the characterisation of defects that are believed to be present in the material, but where it is difficult to