High germanium doping of GaN films by ammonia molecular beam epitaxy
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AbstractGallium Nitride (GaN) grown by ammonia molecular beam epitaxy and doped with elemental Germanium (Ge) is presented. Growth studies varying the GaN growth rate, substrate growth temperature and the elemental Ge flux reveal several incorporation dependencies. Ge incorporation increases with flux, as expected, and a doping range from ∼1017 cm−3 to 1020 cm−3 was readily achieved. A strong substrate temperature dependence on the electrical properties of films grown is observed, with an optimal growth temperature of 740 °C, lower than standard GaN growth conditions for ammonia molecular beam epitaxy. Compensation effects at higher growth temperatures are suspected, as observed with other techniques. Crystallographic defects are apparent at the highest doping concentrations from electrical and optical measurements, however thin layers of such highly doped films are of great interest for contact layers and tunnel junctions in devices.
CitationFireman, M. N., L’Heureux, G., Wu, F., Mates, T., Young, E. C., & Speck, J. S. (2019). High germanium doping of GaN films by ammonia molecular beam epitaxy. Journal of Crystal Growth, 508, 19–23. doi:10.1016/j.jcrysgro.2018.12.009
SponsorsEarly work for this project was funded by the Office of Naval Research through program N00014-15-1-2074 (Paul Maki program manager) and later work by the KACST-KAUST-UCSB Solid State Lighting Program and the CREST program in solid state lighting.
PublisherELSEVIER SCIENCE BV
JournalJOURNAL OF CRYSTAL GROWTH