posted on 2024-09-06, 08:07authored byŁukasz Janicki, Paulina Ciechanowicz, Dominika Majchrzak, Sandeep Gorantla, Robert Kudrawiec, Detlef Hommel
Self-assembled III-nitride columnar structures hold promise
for
enhancing emission efficiency in the UV spectral range. The introduction
of As during molecular beam epitaxial growth of GaN leads to the formation
of microrods with 12 sidewalls arranged in alternating a- and m-planes. This paper investigates the growth
of 12-walled columns to elucidate the nucleation mechanisms, seeding,
and the role of As in growth mode switching. We uncover a dual role
of As: it induces the formation of Ga droplets, serving as the initiation
points for microrod growth, through its antisurfactant effect and
by creating an As-containing shell over the droplets. Observation
of hybrid hexagonal/dodecagonal microrods reveals the necessity of
exposing microrod sidewalls to impinging As for the formation of dodecagonal
columns. This is supported by the observed dodecagonal-to-hexagonal
growth mode switching upon cessation of As supply during growth.