MODELING OF AMORPHOUS ZONES IN SEMICONDUCTORS BY USING THE RANDOMIZATION-AND-RELAXATION METHOD

The structure and stability of isolated amorphous zones, produced by h eavy ion irradiation of semiconductors, has been modeled by using the randomization and relaxation method. The evolution of the temperature and the size of the relaxation volume during annealing process was cal culated by using the thermal spike model. To extend the method to III- V compounds, we used the Martin potential which takes into account the partly ionic character of the atomic bonds. The ''higher-order-neighb ours effective order'' approximation was introduced to permit the elec trostatic part of the potential to be calculated. This model has been used to study the minimum cascade size which is necessary to produce a stable amorphous zone. In addition, an attempt has been made to exami ne the absence of direct-impact amorphization in the ternary alloy Alx Ga1-xAs (with x greater than or similar to 0.5), which is experimental ly observed. No significant difference was found between AlGaAs and Ga As, which we attribute to the simplicity of the Martin potential.