The effect of step-flow growth on the surface morphology and optical properties of thick diamond films

Thick diamond films are needed for high power device applications. One approach is to grow via the step-flow growth mode on miscut substrates. In this paper we correlate variations of surface morphology and optical properties of a 250 μm-thick undoped diamond layer, grown at a rate of 10.4 μm/h, on a (001) diamond substrate with a miscut angle of 10 degrees towards a direction. The epilayer surface comprises regions with island growth on (001) planes, and regions parallel to the miscut substrate surface exhibiting step-bunching and faceting and resulting in various degrees of surface roughness. The optical properties exhibit a combination of sharp and broad luminescence peaks, which are found to be specific to growth morphology and to the nitrogen content in the near-surface region. •Thick diamond films on miscut substrates are investigated.•Significant variations in surface morphology observed associated to step-flow growth.•Nitrogen incorporation near surface due to roughness and step density is observed.•Implications for high-power device applications are discussed.