Dislocation activities in bulk GeSi crystals

The mechanical strength and dislocation velocity in bulk single crystals of GeSi alloy grown by the Czochralski technique were investigated by compressive deformation tests and the etch pit technique, respectively. In the temperature range 450 - 700°C and the stress range 3-24 MPa the dislocation velocity in Ge_1-xSi_x in the composition range x = 0.004-0.080 decreases monotonically with an increase in the Si content, reaching about one seventh of that in pure Ge at x =0.080. The velocity was determined as functions of the stress and the temperature. The stress-strain curve in the yield region of GeSi alloy in the temperature range lower than about 600°C was temperature-sensitive and was similar to those of Ge and Si However, the yield stress of the alloy became temperature-insensitive at high temperatures. It increases with increasing Si content in the composition range x = 0-0.4. The yield stress was dependent on the composition as being proportional to x(1-x). Built-in stress fields in GeSi alloy caused by local fluctuation of the alloy composition together with dynamic development of solute atmosphere around dislocations, are thought to suppress the dynamic activities of dislocations and result in the strengthening of GeSi alloy.