Metastable-like behaviour of a sputter deposition-induced electron trap in n-GaN

We show that a deep level, the ES1, introduced in n-GaN by sputter-deposition of gold Schottky contacts exhibits metastable-like behaviour during temperature cycling between 55 and 250 K. The ES1 has an energy level 0.22 +/- 0.02 eV below the conduction band. We provide some evidence that indicates that the defect responsible for the ES1 has a second energy level, the ES1*, and that the metastable behaviour of the ES1 may be due to negative-U ordering of these two energy levels. Furthermore, held effect measurements indicate that the ES1 level has a donor character, while the ES1* level is probably an acceptor. (C) 1999 Elsevier Science B.V. All rights reserved.