We investigate the triangular defects with different structural features on 4H-SiC epilayers by a Nomarski microscope,a Candela optical surface analyzer and ultraviolet photoluminescence (UV-PL) imaging.Both the foreign particles and the substrate scratches can cause the formation of the obtuse triangular defects.The central area of some obtuse triangular defects can have the spatially confined core,in which the in-grown stacking faults can be observed under the UV-PL imaging.In contrast,the obtuse triangular defects induced by the scratches appear in the form of band-like defects,of which the width depends on the scratch direction and reaches the maximum when the scratch direction is parallel to the step flow direction.The formation mechanisms of these obtuse triangular defects are discussed.