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Characterization of differently grown GaN epilayers by time‐resolved four‐wave mixing technique
Author(s) -
Jarašiūnas K.,
Malinauskas T.,
Aleksiejūnas R.,
Sūdžius M.,
Frayssinet E.,
Beaumont B.,
Faurie J.P.,
Gibart P.
Publication year - 2005
Publication title -
physica status solidi (a)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.532
H-Index - 104
eISSN - 1862-6319
pISSN - 1862-6300
DOI - 10.1002/pssa.200460430
Subject(s) - materials science , dislocation , picosecond , metalorganic vapour phase epitaxy , sapphire , excitation , diffusion , mixing (physics) , carrier lifetime , band gap , optoelectronics , analytical chemistry (journal) , optics , laser , epitaxy , chemistry , silicon , nanotechnology , layer (electronics) , physics , quantum mechanics , composite material , thermodynamics , chromatography
Room temperature time‐resolved four‐wave mixing has been performed in MOCVD GaN epilayers, grown on sapphire substrates by using either conventional or a 3D‐growth mode with Si/N treatment technique (micro‐ELO). Picosecond pulses at 355 nm were used to create light interference pattern and record a spatially modulated carrier distribution by interband transitions, while a delayed probe beam at 1064 nm monitored the carrier dynamics far from the bandgap. The determined values of the bipolar diffusion coefficient and the carrier lifetime were found equal to D a = 1.7–1.8 cm 2 /s and τ R ≈ 1.1 ns for standard grown epilayers, while in the samples with ultralow dislocation density they were found equal to 2.4 cm 2 /s and 2.7 ns. In the interface region of the epilayers with high dislocation density, a dependence of D and τ R values on excitation intensity was found. The latter effect was attributed to a screening of potencial barriers around the charged dislocations by free carriers and an ability of the carriers to become less localized and thus avoid the nonradiative recombination at dislocations. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)