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Time-resolved photoluminescence study of GaN nanowires grown by catalyst-free MBE

Published

Author(s)

John B. Schlager, Kristine A. Bertness, Paul T. Blanchard, Norman A. Sanford

Abstract

We report steady-state and time-resolved photoluminescence (PL & TRPL) measurements on individual GaN nanowires that were grown by nitrogen-plasma-assisted, molecular beam epitaxy on Si(111) and subsequently dispersed onto fused quartz substrates for luminescence measurements. For steady-state PL measurements, samples were pumped with with a HeCd laser (325 nm). For TRPL measurements a frequency tripled mode-locked Ti:Sapphire laser (267 nm) was the pump source and the temporal response of the luminescence was recorded with time-correlated single photon counting . A continuous-He-flow optical cryostat enabled confocal exciatiaon/collection (spatial resolution ~5 um) and control of sample temperatures from < 5 K to 295 K. The dispersed wires (both unintentionally doped and Si-doped) were 6 - 20 um long with diameters of 30 - 500 nm. Separate wire growth batches were examined. Shorter and thinner wires exhibited near-band-edge PL emission peaks at low temperatures (<5 K) associated with both free and bound excitons similar to results reported for strain-free GaN. Longer wires (> 12 um)also exhibited near band edge emission, but with up to 10 times higher PL intensities. The nanowires showed PL lifetimes ranging from 200 ps to over 2 ns. The longer lifetimes are comparable to those reported for low-defect bulk GaN. The decay curves exhibited double exponential or more complex shapes that depended on temperature and excitation intensity, indicating interesting exciton dynamics.
Conference Dates
September 16-21, 2007
Conference Location
Las Vegas, NV
Conference Title
7th International Conference of Nitride Semiconductors

Keywords

gallium nitride, nanowire, photoluminescence, time-resolved photoluminescence

Citation

Schlager, J. , Bertness, K. , Blanchard, P. and Sanford, N. (2007), Time-resolved photoluminescence study of GaN nanowires grown by catalyst-free MBE, 7th International Conference of Nitride Semiconductors, Las Vegas, NV, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=32680 (Accessed June 14, 2024)

Issues

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Created September 16, 2007, Updated February 19, 2017