Suppression and compensation effect of oxygen on the behavior of heavily boron-doped diamond films

This work investigates the suppression and compensation effect of oxygen on the behaviors and characteristics of heavily boron-doped microwave plasma chemical vapor deposition (MPCVD) diamond films. The suppression effect of oxygen on boron incorporation is observed by an improvement in crystal quality when oxygen is added during the diamond doping process. A relatively low hole concentration is expected and verified by Hall effect measurements due to the compensation effect of oxygen as a deep donor in diamond. A low acceptor concentration, high compensation donor concentration and relatively larger acceptor ionization energy are then induced by the incorporation of oxygen; however, a heavily boron-doped diamond film with high crystal quality can also be expected. The formation of an oxygen-boron complex structure instead of oxygen substitution, as indicated by the results of x-ray photoelectron spectroscopy, is suggested to be more responsible for the observed enhanced compensation effect due to its predicted low formation energy. Meanwhile, density functional theory calculations show that the boron-oxygen complex structure is easily formed in diamond with a formation energy of -0.83 eV. This work provides a comprehensive understanding of oxygen compensation in heavily boron-doped diamond.