Mechanical properties of undoped GaAs. III: Indentation experiments

Two types of microindentation experiments, “conventional static” as well as “dynamic displacement-sensitive” tests, have been performed on the (0 0 1) surface of GaAs over a range of temperatures. The temperature dependence of hardness has been measured and, from the disappearance of indentation cracks and the measured energy density at different temperatures, the indentation brittle-to-ductile transition temperature TIBDT has been determined. Comparison of the latter with the conventional brittle-to-ductile transition temperature TBDT by the four-point bend technique indicates that TIBDT is nearly 100 °C lower than TBDT. It is argued that this lowering is because of the superimposed hydrostatic component in an indentation test. The microstructure of the plastic zone around the indentation sites has also been investigated by transmission electron microcopy. Based on the observations, the asymmetry of the dislocation rosettes and indentation cracks is discussed in terms of different mobilities of α and β dislocations in GaAs. Finally, the indentation results are compared with data from compression experiments and 4-point bend tests.