The growth, fabrication, and properties of GaN/AlN/sapphire with periodically poled surface polarity for
second harmonic generation are investigated. The periodic inversion of the surface polarity is achieved by the
growth of a thin AlN buffer layer and subsequent partial removal by using either wet etching with potassium
hydroxide (KOH) or reactive-ion etching (RIE). GaN growth on these substrates by MOCVD leads to Gapolar
GaN on the AlN buffer and N-polar GaN on the bare sapphire. Using atomic force microscopy and
scanning electron microscopy, it is demonstrated that a sufficient combination of H2 and NH3 surface
treatment before the growth of the GaN layers removes surface defects introduced by RIE etching. Thus,
films with comparable quality and properties independent of the etching technique could be grown. However,
in contrast to RIE etching, the interfaces between the Ga-polar and N-polar GaN is rough if KOH etching is
applied. Thus, it is concluded that MOCVD in combination with RIE etched AlN/sapphire substrates can be a
versatile process to fabricate GaN with periodically poled surface polarity as desired for UV light generation
via frequency doubling.
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Marc P. Hoffmann ; Michael Gerhold ; Ronny Kirste ; Anthony Rice ; Christer-Rajiv Akouala, et al.
Fabrication and characterization of lateral polar GaN structures for second harmonic generation
", Proc. SPIE 8631, Quantum Sensing and Nanophotonic Devices X, 86311T (February 4, 2013); doi:10.1117/12.2008827; http://dx.doi.org/10.1117/12.2008827