Aqueous lateral epitaxy overgrowth of ZnO on (0001) GaN at 90 °C: Part I. Increasing the critical thickness
Thick, epitaxial ZnO thin films have been grown on (0001) GaN buffered Al 2O 3 substrates using an aqueous solution at 90 °C. Films with improved structural, optical and electrical characteristics, were grown using a lateral epitaxial overgrowth (LEO) method. Different photoresist masks were used to...
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Published in | Thin solid films Vol. 518; no. 21; pp. 6022 - 6029 |
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Main Authors | , |
Format | Journal Article |
Language | English |
Published |
Amsterdam
Elsevier B.V
01.08.2010
Elsevier |
Subjects | |
Online Access | Get full text |
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Summary: | Thick, epitaxial ZnO thin films have been grown on (0001) GaN buffered Al
2O
3 substrates using an aqueous solution at 90
°C. Films with improved structural, optical and electrical characteristics, were grown using a lateral epitaxial overgrowth (LEO) method. Different photoresist masks were used to enable LEO. The masks included linear windows and two different hexagonal arrays of circular windows. Films that exceeded a critical thickness mechanically failed through buckling, consistent with the large compressive stresses expected due to the mismatch of the ZnO lattice with the underlying GaN substrate. It was shown that improved mechanical stability could be achieved using the LEO method. Without LEO, a film thickness no greater than 4
µm could be grown without buckling. The critical thickness could be increased to 10
µm using linear windows, whereas a critical thickness of 50
μm was achieved with one array of circular windows, and 80
µm for a second array. The two different arrays of circular windows differed relative to their orientation on the substrate. It was also shown that the critical thickness increased with increasing distance between the growth windows. Optical transmission, micro-photoluminescence and Hall Effect measurements showed that the LEO method also results in improved optoelectronic properties. |
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ISSN: | 0040-6090 1879-2731 |
DOI: | 10.1016/j.tsf.2010.03.066 |