On the origin of the electrical activity in silicon grain boundaries

Grain boundaries in silicon are traps for both types of charge carriers. This electrical activity is related to deep levels in the forbidden energy gap, which may have two origins : chemical and extrinsic or structural and intrinsic. Present knowledge on planar symmetric grain boundaries, which are fully reconstructed, induces an extrinsic origin of these levels. However, dangling bonds detected in general grain boundaries indicate that an intrinsic origin of the electrical activity is still possible.