Characterization of differently grown GaN epilayers by time-resolved four-wave mixing technique
| Autor: | Ramūnas Aleksiejūnas, Tadas Malinauskas, Eric Frayssinet, M. Sūdžius, Kęstutis Jarašiūnas, Pierre Gibart, J. P. Faurie, Bernard Beaumont |
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| Rok vydání: | 2005 |
| Předmět: |
Chemistry
Band gap Analytical chemistry Surfaces and Interfaces Carrier lifetime Condensed Matter Physics Molecular physics Surfaces Coatings and Films Electronic Optical and Magnetic Materials Four-wave mixing Picosecond Materials Chemistry Sapphire Metalorganic vapour phase epitaxy Electrical and Electronic Engineering Dislocation Excitation |
| Zdroj: | physica status solidi (a). 202:566-571 |
| ISSN: | 1862-6319 1862-6300 |
| DOI: | 10.1002/pssa.200460430 |
| Popis: | 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. |
| Databáze: | OpenAIRE |
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