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Time‐resolved free carrier lifetime microscopy in bulk GaN
Author(s) -
Šcˇajev Patrik,
Nargelas Saulius,
Jarašiūnas Kęstutis
Publication year - 2013
Publication title -
physica status solidi (rrl) – rapid research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.786
H-Index - 68
eISSN - 1862-6270
pISSN - 1862-6254
DOI - 10.1002/pssr.201307217
Subject(s) - carrier lifetime , photoexcitation , crystallite , picosecond , materials science , diffusion , optoelectronics , microscopy , analytical chemistry (journal) , molecular physics , optics , atomic physics , chemistry , excited state , physics , laser , silicon , chromatography , metallurgy , thermodynamics
A novel setup for lifetime microscopy measurements was designed and applied for carrier lifetime mapping in a bulk GaN. Photoexcitation by a picosecond UV pump and detection of time‐resolved free carrier absorption (FCA) images on a CCD camera enabled the mapping of carrier lifetime distribution with a spatial resolution of 5 μm . The spatial variation of lifetime in the bulk HVPE‐grown GaN revealed the presence of different‐size crystalline grains, with lifetime peaking up to 70 ns in the centers of the largest grains (∼20 μm in diameter) and dropping to 10 ns in the small ones, while the spatially averaged lifetime was 40 ns. The inhomogeneity was ascribed to the interplay of nonradiative diffusion‐limited recombination at grain boundaries and a bulk lifetime in the crystallite centers. The numerical solution of spatially‐resolved carrier decay rate in the crystallite centers at high injection levels and comparison with experimental data provided a bulk nonradiative recombination time of ∼70 ns. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)