Inclination of a threading dislocation in an epilayer of 4H-SiC

Abstract

Threading dislocations (TDs) are inclined from the [0001] c-axis in 4H-SiC epilayers which are produced by the step-controlled technique. The reason for this inclination is discussed in the framework of isotropic elastic theory of dislocation. The elastic strain energy of a TD in an epilayer is calculated as a function of its orientation, and the minimum energy orientation is used to predict the inclination angle. The results of the calculations are as follows. For a cut-off angle (α) of 4°, a threading edge dislocation (TED) and a threading pure screw dislocation (TpSD) are inclined from the c-axis by 12 and 2°, respectively: Threading near screw dislocations (TnSDs) and threading mixed dislocations (TMDs) are inclined by angles ranging from 8 to 15°from the c-axis, depending on their actual Burgers vectors. Similarly for α of 8°, a TED and a TpSD are inclined from the caxis by 21 and 4°, respectively: TnSDs and TMDs are inclined from the c-axis by angles ranging from 7 to 17°. These predictions are in good agreement with experiment.

Behavior of Threading Dislocations from GaN Substrate to Epitaxial Layer

“…Saka et al. also reported that the strain energy of dislocations in the epitaxial layer affects the inclined direction of the dislocations of a TD in SiC . Figure shows a schematic diagram of the dislocation inclination model.…”

“…Figure shows a schematic diagram of the dislocation inclination model. The strain energy ( W E ), when a TD is inclined toward the direction b in the epitaxial layer, is expressed as followswhere d is the thickness of the epitaxial layer, ν is the Poisson's ratio, α is the angle of TD from the growth direction, and γ is the angle formed by the growth plane of the epitaxial layer and b . The value of α that minimizes W E is then determined.…”

3D structure of threading screw dislocation at a deep location in 4H-SiC using 3D micro-X-ray topography

“…TSDs with an inclined angle close to 30°from 〈0001〉 have been theoretically suggested to exist. 12) The propagation of the inclination of TSD from the c-axis was ascertained to be related to the direction of the extra half plane with an a-component by 2PPL. 30) Shinagawa et al 31) estimated that TSD with [1213]/3 of the Burgers vector b had an inclined angle of 26.5°towards the b direction from the c-axis.…”

“…[9][10][11] In terms of isotropic elastic principle, TSD with an inclination of dislocation core-line was predicted to be mixed with either 〈1120〉 (a-) or 〈1100〉 (m-) component. 12) TSDs with only the c-component and including a mixed component were categorized as threading pure screw dislocation (TpSD) and threading mixed dislocation (TMD), respectively. However, our understanding of the relationship between the inclination and mixed component in TSD is limited.…”

Direct observation and three dimensional structural analysis for threading mixed dislocation inducing current leakage in 4H–SiC IGBT

“…[17][18][19][20][21][22] Recently, inclination angle (θ) of TD from the c-axis to the direction of the dislocation line has been recognized as an attractive candidate to distinguish the harmful TD, because electrical properties of TDs are supposed to be almost decided with their Burgers vector (b) and the θ can be calculated as minimum energy state based on the elastic theory in a crystal from b. [23][24][25][26][27] In general, however, it is considered that θ of a particular TD is resulting from motion of a lot of the other dislocations under internal stress in an epitaxial layer during growth where influence of surface cannot be ignored. 5,22) In this study, we fabricated SiC-IGBTs with a considerably thick layer on a 4H-SiC substrate.…”