Secondary ion mass spectrometry investigation of carbon grain formation in boron nitride epitaxial layers with atomic depth resolution

Secondary ion mass spectrometry (SIMS) measurements show that boron nitride (BN) films grown under an argon flow are contaminated with carbon in the form of clusters. SIMS imagining of carbon clusters with atomic depth resolution allows us to show that there are two different growth modes for BN films: 3D growth and self-terminated growth. The choice of the growth mode predominantly depends on reactor pressure. In the 3D growth mode (low pressure) carbon clusters appear in an organized way: the cluster in one BN layer nucleates the one in the successive layer. Eventually, they create three-dimensional carbon grains. In the self-terminated growth mode (high pressure) the distribution of carbon within the volume of the film is chaotic. The differences observed between the growth modes seem to depend on the diffusion length of the carbon and boron species.