A COMPUTER-SIMULATION OF LOCAL AMORPHIZATION IN III-V COMPOUNDS

The formation of amorphous zones, induced by heavy-ion irradiation of III-V compounds and their ternary alloys, was studied using a computer simulation. For this purpose, the so-called sillium model, which has been used to model amorphous Si and Ge, was modified and subsequently employed in III-V compounds. The modification had to take into account different boundary conditions and different interatomic potentials in order to account for the partly ionic character of the bonds in these solids. For the Coulomb part of the potential we assumed rigid point ions with charges equal to the transversal effective charge. The resul ts of the simulation show that the model is capable of producing a loc ally disordered structure surrounded by a perfect crystal lattice, pro vided that the energy of the initial displacement cascade is sufficien tly high. It is also shown that the virtual crystal approximation is n ot adequate to confirm the experimentally observed differences in amor phization between GaAs and Al0.85Ga0.15As.