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Proceedings Paper

Structural Characterization Of Defects In Gaas With Ultrasonic Measurements
Author(s): M. J. Brophy; A. V. Granato
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Paper Abstract

Measurements of ultrasonic attenuation and velocity as a function of temperature can yield valuable structural information on defects which lower the symmetry of the lattice site on which they are located. We report here on two such defects in GaAs: the Cr impurity and the as yet inconclusively identified defects caused by low temperature irradiation with 2.25-2.5 Mev electrons. The neutral Cr impurity (Cr3+-[Ar]3d3) traps an electron to become Cr2+. This charge state undergoes a static tetragonal Jahn-Teller distortion which can be detected ultrasonically. Ultrasonic measurements at 10 frequencies between 5 and 130 MHz for differing polarizations of the stress wave confirm the tetragonal symmetry of the defect, and provide quantatative information on the kinetics of reorientation between energetically equivalent distortions. Samples with as little as .2 appm Cr were studied. Two defects with trigonal symmetry were observed to be created after the above mentioned electron irradiation. Both have reorientation kinetics obeying the Arrhenius law. The frequency factor and activation energy is 1011.5 (1013.2) sec and 12.5 (54.1) meV for the low (high) temperature attenuation peak. Both defects were observed to anneal out below 340 K. The low temperature peak annealed in a complicated fashion between 208 and 334K, whereas the high temperature peak exhibited single activation energy annealing above 320K. Our results suggest that no long range migration of the radiation produced defects occurs below room temperature. There is some evidence that the low temperature attenuation peak could be caused by a Ga vacancy. Several candidates for defects which could be responsible for the high temperature peak are considered and discussed.

Paper Details

Date Published: 26 June 1986
PDF: 5 pages
Proc. SPIE 0623, Advanced Processing and Characterization of Semiconductors III, (26 June 1986); doi: 10.1117/12.961188
Show Author Affiliations
M. J. Brophy, Electronic Decisions Inc. (United States)
A. V. Granato, University of Illinois (United States)

Published in SPIE Proceedings Vol. 0623:
Advanced Processing and Characterization of Semiconductors III
Devindra K. Sadana; Michael I. Current, Editor(s)

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