PLASTICITY OF UNDOPED GAAS DEFORMED UNDER LIQUID ENCAPSULATION

Undoped GaAs single crystals with 〈123〉 orientation are compressed at different strain rates in the temperature range between 730 and 900 °C, using the liquid encapsulation technique to prevent As loss. The resulting stress-strain curves are characterized by five deformation stages, as is known for other semiconductors. From the lower yield point, at high strain rates, an activation energy of 1.37 eV and a stress exponent of 3.6 are deduced; these parameters nearly agree with those obtained earlier at lower temperatures and under a protective atmosphere of argon. At low strain rates deviations occur, whose origin is discussed. The analysis of the first stage of dynamical recovery (stage III), which shows a uniform behavior over the whole temperature and strain-rate range, yields an activation energy of 2.3 eV and a stress exponent of 4.2. These values are discussed in terms of a diffusion-controlled recovery mechanism. The second recovery stage (stage V) probably is governed by cross slip; the cross over of both recovery regimes takes place near 550 °C. The deformation behavior of GaAs is compared to that observed in other semiconductors.