Effects of high temperature annealing on single crystal ZnO and ZnO devices

• Published in: Journal of applied physics 2012-04, Vol.111 (8), p.084503-084503-6
• Main Authors: Mtangi, W., Auret, F. D., Diale, M., Meyer, W. E., Chawanda, A., de Meyer, H., Janse van Rensburg, P. J., Nel, J. M.
• Format: Article
• Language: English
• Subjects: Annealing; Crystal defects; Devices; Electric potential; Energy levels; Leakage current; Voltage; Zinc oxide
• ISSN: 0021-8979; 1089-7550
• DOI: 10.1063/1.3700186

We have systematically investigated the effects of high-temperature annealing on ZnO and ZnO devices using current voltage, deep level transient spectroscopy (DLTS) and Laplace DLTS measurements. Current-voltage measurements reveal the decrease in the quality of devices fabricated on the annealed samples, with the high-temperature annealed samples yielding devices with low barrier heights and high reverse currents. DLTS results indicate the presence of three prominent defects in the as-received samples. Annealing the ZnO samples at 300°C, 500°C, and 600°C in Ar results in an increase in reverse leakage current of the Schottky contacts and an introduction of a new broad peak. After 700°C annealing, the broad peak is no longer present, but a new defect with an activation enthalpy of 0.18 eV is observed. Further annealing of the samples in oxygen after Ar annealing causes an increase in intensity of the broad peak. High-resolution Laplace DLTS has been successfully employed to resolve the closely spaced energy levels.