Femtosecond pump-probe characterization of high-pressure grown AlxGa1-xN single crystals

Jie Zhang; A. Belousov; S. Katrych; J. Jun; J. Karpinski; B. Batlogg; Roman Sobolewski

doi:10.1117/12.813413

19 February 2009 Femtosecond pump-probe characterization of high-pressure grown Al_xGa_1-xN single crystals

Jie Zhang, A. Belousov, S. Katrych, J. Jun, J. Karpinski, B. Batlogg, Roman Sobolewski

Proceedings Volume 7216, Gallium Nitride Materials and Devices IV; 721623 (2009) https://doi.org/10.1117/12.813413
Event: SPIE OPTO: Integrated Optoelectronic Devices, 2009, San Jose, California, United States

Abstract

We report our experimental studies on the time-resolved dynamics of conduction electrons in high quality Al_xGa_1-xN single crystals. The Al_xGa_1-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 Al_xGa_1-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.

Citation Download Citation

Jie Zhang, A. Belousov, S. Katrych, J. Jun, J. Karpinski, B. Batlogg, and Roman Sobolewski "Femtosecond pump-probe characterization of high-pressure grown Al_xGa_1-xN single crystals", Proc. SPIE 7216, Gallium Nitride Materials and Devices IV, 721623 (19 February 2009); https://doi.org/10.1117/12.813413

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