Laser-assisted atom probe tomography of MBE grown GaN nanowire heterostructures
Norman A. Sanford, Paul T. Blanchard, Matthew D. Brubaker, Kristine A. Bertness, John B. Schlager, R Kirchofer, David R. Diercks, Brian Gorman
Laser-assisted atom probe tomography (L-APT) was performed on GaN nanowires (NWs) and axial GaN/InGaN nanowire heterostructures. All samples were grown by MBE on Si(111) substrates. The laser pulse energy (PE) at 355 nm used in L-APT analysis of GaN NWs was re-stricted to the range of 2‒10 pJ in order to recover the correct GaN stoichiometry within experimental uncer-tainty. Higher PE at 355 nm generally returns an apparent (but unphysical) deficit in N composition under L-APT analysis of GaN. Axial GaN/InGaN NW heterostructures were also grown by MBE. In these experiments a GaN NW segment was first grown at 820 ° C followed by GaN-capped InGaN maker layers grown variously at 585 °C and 615 °C. The capped InGaN markers were separated by GaN spacer layers. Different growth schedules were explored for growth of the GaN spacers where the N and Ga fluxes were maintained but the tem-perature was raised 820 °C in some cases but held con-stant in others. L-APT revealed that raising the tempera-ture for the growth of the GaN spacers resulted in diffu-sion of In. These observations were corroborated by HRTEM. Moreover, L-APT performed on the GaN/InGaN NWs with PE = 2 pJ revealed that regions with dispersed In showed an (unphysical) N deficit but regions where the InGaN marker layers remained localized showed approximately correct stoichiometry. However, even in cases where the In markers remain localized, background In was still found between the markers
, Blanchard, P.
, Brubaker, M.
, Bertness, K.
, Schlager, J.
, Kirchofer, R.
, Diercks, D.
and Gorman, B.
Laser-assisted atom probe tomography of MBE grown GaN nanowire heterostructures, Physica Status Solidi
(Accessed December 7, 2021)