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High sensitivity of Franz-Keldysh oscillations in photoreflectance spectra for probing morphology in Alx Ga 1−x N/GaN heterostructures

Published online by Cambridge University Press:  17 January 2007

H. Takeuchi ,
Y. Yamamoto ,
Y. Kamo ,
T. Kunii ,
T. Oku ,
S. Wakaiki  and
M. Nakayama
H. Takeuchi*
Affiliation:
R & D Department, High Frequency and Optical Device Works, Mitsubishi Electric Corporation, 4-1 Mizuhara, Itami, Hyogo 664-8641, Japan
Y. Yamamoto
Affiliation:
R & D Department, High Frequency and Optical Device Works, Mitsubishi Electric Corporation, 4-1 Mizuhara, Itami, Hyogo 664-8641, Japan
Y. Kamo
Affiliation:
R & D Department, High Frequency and Optical Device Works, Mitsubishi Electric Corporation, 4-1 Mizuhara, Itami, Hyogo 664-8641, Japan
T. Kunii
Affiliation:
R & D Department, High Frequency and Optical Device Works, Mitsubishi Electric Corporation, 4-1 Mizuhara, Itami, Hyogo 664-8641, Japan
T. Oku
Affiliation:
R & D Department, High Frequency and Optical Device Works, Mitsubishi Electric Corporation, 4-1 Mizuhara, Itami, Hyogo 664-8641, Japan
S. Wakaiki
Affiliation:
Department of Applied Physics, Graduate School of Engineering, Osaka City University, 3-3-138 Sugimoto, Sumiyoshi-ku, Osaka 558-8585, Japan
M. Nakayama
Affiliation:
Department of Applied Physics, Graduate School of Engineering, Osaka City University, 3-3-138 Sugimoto, Sumiyoshi-ku, Osaka 558-8585, Japan
*
[email protected]
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Abstract

We demonstrate that Franz-Keldysh oscillations (FKOs) observed by photoreflectance (PR) spectroscopy are highly sensitive to the surface morphology of Alx Ga1−x N layers in Alx Ga1−x N heterostructures. Three Al0.2Ga0.8N/GaN heterostructures with different surface-morphology profiles, which are confirmed with atomic force microscopy, have been investigated. The X-ray-diffraction patterns are hardly affected by the Al0.2Ga0.8N/GaN-layer morphology. In contrast, it is revealed that cracks and pits dominating the morphology remarkably reduce the amplitude of the FKOs from the Al0.2Ga0.8N/GaN layer, which is attributed to the following two mechanisms related to the cracks and pits. One is lifetime broadening due to carrier scattering, and the other is the suppression of the modulation magnitude for the built-in electric field, which is caused by the trapping and recombination of photogenerated carriers at the surface.

Keywords

Type
Research Article
Information
The European Physical Journal - Applied Physics , Volume 37 , Issue 2 , February 2007 , pp. 119 - 122
Copyright
© EDP Sciences, 2007

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