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Proceedings Paper

Femtosecond pump-probe characterization of high-pressure grown AlxGa1-xN single crystals
Author(s): Jie Zhang; A. Belousov; S. Katrych; J. Jun; J. Karpinski; B. Batlogg; Roman Sobolewski
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Paper Abstract

We report our experimental studies on the time-resolved dynamics of conduction electrons in high quality AlxGa1-xN single crystals. The AlxGa1-xN synthesis with the Al content of up to 90% was performed using a solution growth technique in a high nitrogen pressure system, maintained for several days under the high (up to 15 kBar) gas pressure and at very high (up to 1800°C) temperatures. The resulting crystals were colorless (fully transparent to visible light) platelets up to ~1 mm2 in size, and exhibited a hexagonal Würtzite structure. Our optical measurements were performed at room temperature, using a two-color (ultraviolet and near-infrared), femtosecond, pump-probe spectroscopy, by invoking a two-photon, volume absorption and scanning the normalized transient differential transmitivitty (ΔT/T) signal of the probe beam. The observed ΔT/T signal was a superposition of a femtosecond, two-photon-absorption (TPA) correlation transient and a conventional optical pump-probe photoresponse signal with a rise time of ~1 ps and decay of ~75 ps. We have found that the TPA process was quite efficient with the absorption coefficient β ≈ 0.337 cm/GW at 380 nm, and enabled us to directly determine that the optical bandgap of AlxGa1-xN (x = 0.86) was 5.81 +/-0.01 eV. The latter value is in the good agreement with the one deduced from the x-ray diffraction measurements.

Paper Details

Date Published: 19 February 2009
PDF: 9 pages
Proc. SPIE 7216, Gallium Nitride Materials and Devices IV, 721623 (19 February 2009); doi: 10.1117/12.813413
Show Author Affiliations
Jie Zhang, Univ. of Rochester (United States)
A. Belousov, ETH Zürich (Switzerland)
S. Katrych, ETH Zürich (Switzerland)
J. Jun, ETH Zürich (Switzerland)
J. Karpinski, ETH Zürich (Switzerland)
B. Batlogg, ETH Zürich (Switzerland)
Roman Sobolewski, Univ. of Rochester (United States)

Published in SPIE Proceedings Vol. 7216:
Gallium Nitride Materials and Devices IV
Hadis Morkoç; Cole W. Litton; Jen-Inn Chyi; Yasushi Nanishi; Joachim Piprek; Euijoon Yoon, Editor(s)

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