Speaker
Description
Studies on point defects in germanium (Ge) are increasing, primarily because these defects have the potential to modify the electronic and optical properties of Ge, thereby enhancing device applications. While significant progress has been made in defect studies, a comprehensive understanding of defect complexes resulting from interactions between type (Al or B) and p-type atoms (D_GeX_i and DX; where D = Al, B, and X = N, P, As, Sb) is still lacking. Therefore density functional theory calculations of electrically active defect levels in Ge that are caused by interactions between n-type impurity atoms and Al or B, are presented. For defect-complexes formed by Al and n-type atoms, Al and P exhibit the highest formation stability under equilibrium conditions. Conversely, B_GeP_i represents the most energetically favorable defect-complex. With the exception of B_GeN_i, the energetic stability of all defect-complexes suggests that Al and B interstitials form strong bonds with n-type substitutional atoms. Electrical behavior analyses of these defects reveal that defect-complexes formed by Al and n-type atoms induce deep defect levels. Specifically, Al_GeN_i acts as an acceptor, while Al_iAs_Ge behaves as a donor. The defects B_GeSb_i, B_iP_Ge, and B_iAs_Ge donate electrons to the conduction band at energy levels within the range of 3 KbT. Furthermore, B_GeSb_i induces shallow donor levels, whereas B_GeP_i induces acceptor levels. This study opens new research opportunities in the experimental synthesis of defects and offers insights into controlling them, potentially enhancing electronic devices.
