Effects of N2 partial pressure on Growth, Structure, and Optical Properties of GaN Nanorods Grown by Liquid-target Reactive Magnetron Sputter Epitaxy
(English)Manuscript (preprint) (Other academic)
GaN nanorods, essentially free from crystal defects and exhibiting very sharp band-edge luminescence, have been grown by reactive direct current magnetron sputter epitaxy onto Si(111) substrates at a low pressure of 5 mTorr. Upon diluting the reactive N2 working gas by a small amount of Ar (0.5 mTorr), we observe an increase in nanorod aspect ratio from 8 to ~35, a decrease in average diameter from 74 nm to 35 nm, and a 2-fold increase in nanorod density. By further dilution, the aspect ratio continuously decreases to 14 while the diameter increases to 60 nm and the nanorod density increases to a maximum of 2.4×109 cm-1. Lower N2 partial pressures lead to continuous GaN films. The morphological dependence on N2 partial pressure is explained by a change from N-rich to Ga-rich growth conditions, combined with a reduced GaN-poisoning of the Ga-target, as the N2 gas pressure is reduced. Nanorods grown at 2.5 mTorr N2 partial pressure exhibit a high intensity 4 K photoluminescence D0XA peak at ~3.479 eV with a full-width-at-half-maximum of 1.7 meV. High-resolution transmission electron microscopy confirms the excellent crystalline quality of the nanorods already implied by the good PL data.
GaN, Nanorods, X-ray Diffraction, TEM, PL, Magnetron Sputter Epitaxy, Sputtering
IdentifiersURN: urn:nbn:se:liu:diva-84654OAI: oai:DiVA.org:liu-84654DiVA: diva2:560992