Efficient polarity recognition in p-type 4H-SiC single crystals using pull-off force signatures

Abstract

As a representative of third-generation semiconductor materials, 4H-SiC demonstrates immense potential in power electronic applications. Particularly, 4H-SiC-based n-channel insulated gate bipolar transistors (n-IGBTs) have emerged as pivotal components for ultrahigh voltage applications (>10 kV). As the basic material for fabricating these devices, p-type 4H-SiC substrates inherently exhibit two distinct polar faces (Si-face and C-face) with divergent surface properties. These polarity-dependent characteristics critically impact crystal growth, crystal machining, and device fabrication. Precise recognition of polar faces of p-type 4H-SiC single crystals is indispensable for these correlated processes. However, traditional polarity recognition methods remain constrained by vacuum dependence, destructive sample processing, and accuracy limitations. Here, we demonstrate an efficient atomic force microscopy (AFM)-based method to recognize the polar faces of p-type 4H-SiC single crystals through distinct pull-off force signatures. This method can be performed under ambient conditions without causing sample damage, while maintaining high reliability. Experimental results reveal that the Si-face exhibits a 75% higher average pull-off force than the C-face, exhibiting a substantial difference between the polar faces. Detailed calculations demonstrate that van der Waals interaction accounts for over 90% of the total pull-off force, while capillary force contributes less than 10%. The Si-face's stronger surface energy significantly enhances its van der Waals interaction, thereby resulting in greater pull-off force on the Si-face. By providing a simple, non-destructive, and reliable solution, this method enables efficient recognition of polar faces of p-type 4H-SiC single crystals through distinguishable pull-off force. Furthermore, this methodology can be extended to the study of other polar materials.