AMORPHIZATION FROM THE QUENCHED HIGH-PRESSURE PHASE IN TETRAHEDRALLY-BONDED MATERIALS

X-ray diffraction of GaAs and InAs has been measured at pressures up t o 25 GPa and at temperatures down to 90 K by an energy dispersive meth od using synchrotron radiation. When pressure was released at low temp erature, the metallic high-pressure phase was quenched. In GaAs, amorp hization from the quenched high-pressure phase occurs from 140 to 260 K when temperature is increased at 5 GPa, and from 170 to 270 K at 8 G Pa. Similar amorphization occurs on decompression at 160 and 220 K. In InAs, phase transition from the quenched high-pressure phase to a mic ro-crystalline zinc-blende phase occurs when temperature is increased at 2.5, 2.0 and 1.5 GPa. These results are discussed in connection wit h the pressure dependence of potential barriers for the phase transiti ons by using a configuration-coordinate model. The effects of strength and ionicity of bonds on amorphization are also discussed in connecti on with the phase transitions in other tetrahedrally-bonded materials.