Doping-limitations of cubic boron nitride: effect of unintentional defects on shallow doping

Cubic boron nitride (cBN) is an ultra-wide bandgap material with potential for extreme temperature and pressure applications. Although, a p-n junction using this material was demonstrated almost three decades ago, full potential of cBN in device applications has not been realized. Two main hurdles are difficulties in producing high-quality cBN films and controllable n- and p- doping its matrix. In this theoretical work, we study the reasons for doping-limitations, an acute issue in realizing cBN-based electronics. We find that different intrinsic and extrinsic defects act as compensating defects and/or introduce trap states. Amongst different foreign impurities, we explored defects containing carbon and oxygen, as large numbers of these impurities are detected in as-grown cBN. We find that the unintentional defects and their complexes not only affect the incorporation of the shallow dopants [silicon and beryllium], but also can introduce deep trap states, which will adversely affect cBN-based devices. Our analysis of doping-limitations due to unintentional defects/impurities is an important step towards finding solutions for controllably n- or p-doping cBN.