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Open Access Nano Express

Ultrafast Carrier Relaxation in InN Nanowires Grown by Reactive Vapor Transport

Andreas Othonos1*, Matthew Zervos2 and Maria Pervolaraki2

Author Affiliations

1 Department of Physics, Research Centre of Ultrafast Science, University of Cyprus, P.O. Box 20537, 1678, Nicosia, Cyprus

2 Department of Mechanical Engineering, Materials Science Group, University of Cyprus, P.O. Box 20537, 1678, Nicosia, Cyprus

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Nanoscale Research Letters 2008, 4:122-129  doi:10.1007/s11671-008-9211-8

Published: 26 November 2008

Abstract

We have studied femtosecond carrier dynamics in InN nanowires grown by reactive vapor transport. Transient differential absorption measurements have been employed to investigate the relaxation dynamics of photogenerated carriers near and above the optical absorption edge of InN NWs where an interplay of state filling, photoinduced absorption, and band-gap renormalization have been observed. The interface between states filled by free carriers intrinsic to the InN NWs and empty states has been determined to be at 1.35 eV using CW optical transmission measurements. Transient absorption measurements determined the absorption edge at higher energy due to the additional injected photogenerated carriers following femtosecond pulse excitation. The non-degenerate white light pump-probe measurements revealed that relaxation of the photogenerated carriers occurs on a single picosecond timescale which appears to be carrier density dependent. This fast relaxation is attributed to the capture of the photogenerated carriers by defect/surface related states. Furthermore, intensity dependent measurements revealed fast energy transfer from the hot photogenerated carriers to the lattice with the onset of increased temperature occurring at approximately 2 ps after pulse excitation.

Keywords:
InN Nanowires; Carrier dynamics; Femtosecond differential absorption spectroscopy; Absorption edge; Reactive vapor transport