We present low temperature cathodoluminescence (CL) characterization of non-polar GaN epitaxial lateral overgrowth (ELO) structures at various growth stages. The a-plane GaN ELO was grown on a-plane GaN template on r-plane sapphire by metal organic chemical vapor deposition (MOCVD). A 50 nm SiO2 mask with 4 µm mask / 6 µm window regions was used for selective growth aligned along the c-direction. Growth was promoted vertically out of the mask openings with a shift to lateral promoting growth by halving the V/III ratio of precursors. Finally, the structures were capped by an AlGaN layer.
The distinctly different growth domains of a-plane ELO GaN on stripe masks oriented along c-direction were directly visualized by highly spatially and spectrally resolved cathodoluminescence microscopy.
Distinct microscopic regions dominated by differing individual peak wavelengths originating from either basal plane stacking faults, prismatic stacking faults, impurity related donor-acceptor pair or (D0,X) emission as well as yellow luminescence are explicitly correlated to the different growth domains. A strong increase in luminescence intensity from the ELO wings in comparison to the coherently grown region is observed.
A 70 nm AlGaN film of 30% Al-concentration was deposited on a coalesced GaN ELO sample and hydride vapor phase epitaxy (HVPE) grown bulk GaN film by MOCVD. A comparison of the luminescence properties was made to probe the growth quality of the overgrown layer and AlGaN/GaN interface.
Acknowledgement: This work was supported by the National Science Foundation under Grant no. DMR-1309535.
Kasey Hogan, Sebastian Metzner, Frank Bertram, Isra Mahaboob, Emma Rocco, F. Shahedipour-Sandvik, Anja Dempewolf, and Jürgen Christen, "A-plane GaN epitaxial lateral overgrowth structures: growth domains, morphological defects, and impurity incorporation directly imaged by cathodoluminescence microscopy (Conference Presentation)," Proc. SPIE 10532, Gallium Nitride Materials and Devices XIII, 105320V (Presented at SPIE OPTO: January 30, 2018; Published: 14 March 2018); https://doi.org/10.1117/12.2290249.5751529195001.
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