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RESEARCH PAPERS: Heat Conduction in Thin Films

Thermal Diffusivity Measurement of GaAs/AlGaAs Thin-Film Structures

[+] Author and Article Information
G. Chen

Department of Mechanical Engineering and Materials Science, Duke University, Durham, NC 27708

C. L. Tien

Department of Mechanical Engineering, University of California, Berkeley, CA 94720

X. Wu, J. S. Smith

Department of Electrical Engineering and Computer Science, University of California, Berkeley, CA 94720

J. Heat Transfer 116(2), 325-331 (May 01, 1994) (7 pages) doi:10.1115/1.2911404 History: Received April 01, 1993; Revised August 01, 1993; Online May 23, 2008

Abstract

This work develops a new measurement technique that determines the thermal diffusivity of thin films in both parallel and perpendicular directions, and presents experimental results on the thermal diffusivity of GaAs/AlGaAs-based thin-film structures. In the experiment, a modulated laser source heats up the sample and a fast-response temperature sensor patterned directly on the sample picks up the thermal response. From the phase delay between the heating source and the temperature sensor, the thermal diffusivity in either the parallel or perpendicular direction is obtained depending on the experimental configuration. The experiment is performed on a molecular-beam-epitaxy grown vertical-cavity surface-emitting laser (VCSEL) structure. The substrates of the samples are etched away to eliminate the effects of the interface between the film and the substrate. The results show that the thermal diffusivity of the VCSEL structure is 5–7 times smaller than that of its corresponding bulk media. The experiments also provide evidence on the anisotropy of thermal diffusivity caused solely by the effects of interfaces and boundaries of thin films.

Copyright © 1994 by The American Society of Mechanical Engineers
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