Cathodoluminescence of ZnO/GaN/α-Al2O3 heteroepitaxial structures grown by chemical vapor deposition

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Abstract
The cathodoluminescent properties of ZnO films in ZnO/GaN/α-Al2O3 and ZnO/α-Al2O3 heteroepitaxial structures grown by chemical vapor deposition in a low-pressure flowing-gas reactor were studied and compared. A superlinear dependence of the excitonic-band intensity in the cathodoluminescence spectrum of the ZnO/GaN/α-Al2O3 structures on the electron-beam current is ascertained, which indicates that the emission is stimulated for relatively low thresholds of the excitation intensity. It is shown that the ZnO films grown on the GaN substrates exhibit a much more effective cathodoluminescence compared to the cathodoluminescence in the films grown on α-Al2O3. It was observed that the luminescent properties of ZnO layers in the ZnO/GaN/α-Al2O3 structures subjected to long-term heat treatment at 750°C in an oxygen atmosphere exhibit a high thermal stability.