Mechanical properties of undoped GaAs. II: The brittle-to-ductile transition temperature

In this second part of a series of papers on the mechanical properties of GaAs, direct determination of the brittle-to-ductile transition temperature T-BDT of the same crystal as that used for compression experiments (see part I) is reported. The experimental technique employed for this purpose is four-point bend testing of pre-cracked samples at different temperatures and strain rates. It is found that, as in other semiconductors, TBDT of GaAs is sharp, and is very sensitive to and increases with the strain rate from 300 to 380 degrees C for the strain rate ranging from (epsilon) over dot = 1 X 10(-6) s(-1) to (epsilon) over dot = 5 x 10(-5) s(-1). From the variations of TBDT with the strain rate, the activation enthalpy Delta H-d for dislocation glide in undoped GaAs was determined to be 1.36 +/- 0.02 eV, a value very close to that reported for the slow P dislocations in such a crystal. (c) 2007 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.