Bulk-Like Properties Observed From High Density GaN Nanocolumns Grown by Molecular Beam Epitaxy
J E. Van Nostrand, R Cortez, J Boecki, J D. Albrecht, C E. Stutz, K L. Averett, Norman Sanford, Albert Davydov
Vertical GaN nanocolumns (NCs) having a width of 90+10 nm and a length of the film thickness were grown by plasma-assisted molecular beam epitaxy on Al_subscript 2)O_subscript 3} (0001). Low temperature photo-luminescence measurements of NC films results are compared to photoluminescence from typical continuous GaN epitaxial layers. Excitonic emission from NC films were dominated by a high intensity peak with an extremely narrow full width at half max, measuring only 1.37 Angstroms and centered at 3571.8 Angstroms. This peak is identified as the ground state of the A free exciton. The near delta exciton line width reflects the extraordinarily high crystalline quality of these heterogeneous films grown on lattice mismatched substrates. The dense packing of the NCs give them the appearance of a continuous film in surface view. However, Hall effect and scanning electron microscopy measurements indicate the individual NCs are electrically isolated laterally, and exhibit essentially defect free, bulk like properties in their luminescence and microstructure. Detailed analysis using cross-sectional transmission electron microscopy and X-ray reflection on the GaN NC films identifies the microstructure as wurtzite GaN and reveal a surprisingly low defect density within the NCs. The GaN NCs are subsequently utilized as an approximately defect free quasi-substrate for optical studies of silicon dopant and InGaN/GaN multi-quantum well layer structures. Significant improvements in quantum well photoluminescence emission intensity and line width are observed for optical structures grown on NCs in comparison to standard thin films grown by MBE. A 311 meV blue shift in the quantum well emission is also observed for quantum wells grown on NC mate
Physical Review B (Condensed Matter and Materials Physics)
GaN, photoluminescence, semiconductor nanowires
Van Nostrand, J.
, Cortez, R.
, Boecki, J.
, Albrecht, J.
, Stutz, C.
, Averett, K.
, Sanford, N.
and Davydov, A.
Bulk-Like Properties Observed From High Density GaN Nanocolumns Grown by Molecular Beam Epitaxy, Physical Review B (Condensed Matter and Materials Physics)
(Accessed February 23, 2024)