Birefringence images of micropipes viewed end-on in 6H-SiC single crystals

Abstract

The nature of the micropipe, a fatal defect in SiC-based device applications, is still not fully understood. In this work, the birefringence images of micropipes in 6H-SiC crystals along the c axis have been observed and simulated in detail. Based on Frank's theory, the intensity contours of birefringence images for micropipes viewed end-on in 6H-SiC crystals have been derived by considering the photoelastic anisotropy of silicon carbide. The results are in good agreement with experimental observations. research papers J. Appl. Cryst. (2008). 41, 939-943 Lina Ning et al. Birefringence images of micropipes 943

Progress in research of GaN-based LEDs fabricated on SiC substrate

“…Ning et al [20] observed and simulated the birefringence images of micropipes in 6H-SiC crystals. Based on Frank's theory, the intensity contours of birefringence images for micropipes viewed end-on in SiC crystals has been derived by considering the photoelastic anisotropy of silicon carbide.…”

“…Figure 4 shows a microscopic image of a micropipe observed by a polarizing optical microscope and the corresponding simulation image. [20] According to the above discussion, a series of measures were taken. A significant reduction in micropipe density was achieved.…”

“…4. (color online) Birefringence image of a micropipe observed by a polarizing optical microscope and the corresponding simulation image shown in the inset at the upper right [20].…”

Investigation of reflection anisotropy induced by micropipe defects on the surface of a 4H-SiC single crystal using scanning anisotropy microscopy

“…Moreover, microstructural defects in the semiconductor material directly affect the quality of epitaxial material and the performance of devices, especially high-power devices. [9][10][11][12] In addition to solving the problems of reducing or eliminating microstructural defects such as dislocations and micropipes, it is more important to have a thorough understanding of their formation mechanism. The formation mecha-nism of micropipes is widely recognized by Frank's theory, [13] which interprets this formation mechanism as the stress relaxation of screw dislocations with large Burgers vectors.…”

“…Recently, Ning et al proposed a hypothesis based on the fact that micropipes are pure screw dislocations to explain the stress birefringence imaging of micropipes. [9] However, Presser, Vetter and Ouisse have demonstrated that the micropipes contain not only screw dislocations with large Burgers vectors but also edge dislocation components by using conventional polarizing microscopy, transmission electron microscopy (TEM) and high-resolution x-ray diffraction (XRD). [14][15][16][17] Therefore, controversies still exist over the formation mechanism of micropipes, and it is of great significance to develop a suitable and nondestructive evaluation technique that can fully characterize the micropipe defects and study their formation mechanism, thus providing guidance for the growth of materials.…”