Effect of Dopant Concentrations and Annealing Conditions on the Electrically Active Profiles and Lattice Damage in Al Implanted 4H-SiC

This paper reports on the electrical activation and structural analysis of Al implanted 4H-SiC. The evolution of the implant damage during high temperature (1650 - 1700 degrees C) annealing results in the presence of extended defects and precipitates, whose density and depth distribution in the implanted sheet was accurately studied for two different ion fluences (1.3x10(14) and 1.3x10(15) cm(-2)) by transmission electron microscopy. Furthermore, the profiles of electrically active Al were determined by scanning capacitance microscopy. Only a limited electrical activation (similar to 10%) was measured for both fluences in the samples annealed without a capping layer. The use of a graphite capping layer to protect the surface during annealing showed a beneficial effect, yielding both a reduced surface roughness and an increased electrical activation (similar to 20% for the highest fluence and 30% for the lowest one) with respect to samples annealed without the capping layer.