Decoupling of a strained 3C-SiC(111) thin film on silicon by He+ and O+ ion implantation

This paper reports the successful reduction of tensile strain in a thin ion-beam-synthesized 3C-SiC(111) layer on silicon. Significant relaxation is achieved by creating a near-interface defect structure containing nanometric voids and dislocation loops by the implantation of He ions and subsequent thermal annealing. The structural features of this defect microstructure are investigated by transmission electron microscopy. High-resolution X-ray diffraction in a parallel beam configuration is used to quantify the strain state of the top SiC layer. Further annealing experiments were carried out in order to emulate typical process conditions for the growth of wide-bandgap semiconductors like, for example GaN. It is found that prolonged annealing at elevated temperatures leads to coarsening of the voids and to a much less efficient strain reduction. We show that this issue can be resolved by the co-implantation of oxygen to form highly thermally stable cavity/extended defect structures. The technique presented here may be useful for a variety of other thermally mismatched bulk/thin film couples as well.