Thermally stable ZnO films deposited on GaAs substrates with a SiO2 thin buffer layer

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Abstract
SiO2 thin films (1000‐Å thick) were sputter deposited on GaAs substrates as a buffer layer in order to alleviate a thermal mismatching problem between ZnO films and GaAs substrates. Thermal stability of sputter‐deposited ZnO films (0.5–2.0 μm thick) was tested on such a buffered GaAs substrate with a postdeposition heat treatment at 430 °C for 10 min, which is similar to a standard ohmic contact alloying condition. The films sustained the heat treatment well, not showing any crumbling, which has usually been a problem when a ZnO film is deposited directly on a GaAs substrate. The postdeposition anneal treatment also dramatically enhances c‐axis orientation of the ZnO films and relieves intrinsic stress almost completely. These improvements are attributed to a reduction of grain boundaries and voids with the anneal treatment as supported by the scanning electron microscopy and x‐ray diffraction measurement results.