Wurtzite vs zinc blende phase selection in GaN nanowires

Due to the difference between the bandgap value of wurtzite and zincblende GaN variants, the realization of homo-epitaxial wurtzite/zincblende GaN heterostructures has been considered for long as an attractive possibility to grow optoelectronic devices exhibiting a reduced internal electric field. In accordance with this goal, we show that controlled phase selection can be achieved in GaN nanowire heterostructures, taking advantage of the absence of extended defects acting as extrinsic nucleation centers. Zinc blende GaN nanowire sections were grown in the Ga-rich regime at low temperatures while wurtzite sections were grown at high temperatures in slightly N-rich conditions. High resolution scanning electron microscopy experiments demonstrate atomically flat interfaces, opening the path to the realization of homo-epitaxial optoelectronic devices emitting in the UV-A wavelength range.