Nucleation conditions for catalyst-free GaN nanowires
Kristine A. Bertness, Alexana Roshko, Lorelle Mansfield, Todd E. Harvey, Norman Sanford
We have examined the initial steps for catalyst-free growth of GaN using molecular beam epitaxy on Si (111) substrates using AlN buffer layers. These wires form spontaneously under high N-to-Ga ratios for a growth temperature range of about 810 to 830 °C. Field emission scanning electron microscopy (FESEM) shows that part of the GaN forms a "matrix layer" that also grows with the [0 0 0 1] direction perpendicular to the substrate surface. This layer contains small, dense hexagonal pits in which the nanowires nucleate. Using both FESEM and atomic form microscopy (AFM), we identify the pit facets as 1 0 -1 2} planes. The nucleation studies show that the use of an AlN buffer layer is essential to the regular formation of the nanowires and matrix layers under our growth conditions. Our typical AlN buffer layer is 40-50 nm thick. We conclude that the nucleation mechanism for nanowires includes formation of nanocolumns in the AlN buffer layer. The propagation of the nanowires in GaN growth appears to be driven by differences in growth rates among crystallographic planes under N-rich conditions.
, Roshko, A.
, Mansfield, L.
, Harvey, T.
and Sanford, N.
Nucleation conditions for catalyst-free GaN nanowires, Journal of Crystal Growth, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=32346
(Accessed November 30, 2023)