| AVS 57th International Symposium & Exhibition | |
| Electronic Materials and Processing | Tuesday Sessions |
| Session EM-TuM |
| Session: | Contacts and Transport |
| Presenter: | M.W. Allen, University of Canterbury, New Zealand |
| Authors: | M.W. Allen, University of Canterbury, New Zealand S.M. Durbin, University at Buffalo |
| Correspondent: | Click to Email |
Zinc oxide is an interesting test case for evaluating theoretical Schottky contact formation models as it is significantly more ionic than most semiconductors. This results in weaker Fermi level pinning, which in turn allows the barrier height of Schottky contacts to vary with metal properties. Equally important is the fact that contacts can be prepared on laterally homogeneous, bulk-grown, single crystals with minimal surface processing as there is no requirement, as with most semiconductors, to remove native surface oxide layers with potentially damaging etching treatments. As a result, we have been able to fabricate very low ideality factor, laterally homogeneous Schottky contacts to ‘intrinsic’ ZnO surfaces for a wide variety of metals using a novel eclipse pulsed laser deposition technique. Using these contacts, we have evaluated the two leading contemporary Schottky contact formation models – Tung’s ‘chemical bond polarization model’ and Mönch’s ‘metal induced gap states and electronegativity model’. The lack of broad agreement with either of these models suggests the involvement of additional mechanisms, perhaps involving the large spontaneous polarization of ZnO and ionic surface charge screening effects, with important consequences for other oxide semiconductors.