Analysis and modeling of localized faceting on 4H-SiC epilayer surfaces

Comparing with the well-established theory of periodic surface faceting, the formation mechanism of localized surface faceting is not yet clear. We investigate the localized surface faceting of 4H silicon carbide (4H-SiC) epilayers using atomic force microscopy (AFM). The AFM measurements reveal that this phenomenon gives rise to the appearance of isolated macrosteps with multiple unit cell heights. A model for the localized surface faceting is presented based on the AFM cross-sectional height profile. In this model, the isolated macrostep appears in the form of the double-hill–valley structure. We formulize the total surface free energy in the model and explain the important structural features of isolated macrosteps observed by AFM. A generalized model for the localized surface faceting with multiple-hill–valley structure is further proposed to analyze the transition from the localized surface faceting to the periodic surface faceting. Our results provide a basis for understanding the localized surface faceting phenomenon of 4H-SiC epilayers.