LOCAL PHASE-TRANSITION IN GAP AND GAAS ANALYZED USING INTERNAL-FRICTION AND YOUNGS MODULUS DATA

Two maxima of internal friction can be found near 320 K (peak I) or ne ar 380 K (peak II), respectively, in GaAs (only peak I) and GaP at ult rasonic frequencies near 105 kHz. Peak II can be attributed to some po int defect relaxation mechanism, whereas peak I can be explained by a local phase transition that can occur in the stress field of dislocati ons moved by ultrasonic deformation. Numerical analysis of the measure d Young's modulus yields a reaction order for the transition of 0.69 a nd an activation energy of 113 kJ/mol.