Synchrotron Topography Studies of Growth and Deformation-Induced Dislocations in 4H-SiC
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Synchrotron Topography Studies of Growth and Deformation-Induced Dislocations in 4HSiC M. Dudley1, H. Wang1, F. Wu1, S. Byrappa1, S. Shun 1, B. Raghothamachar1, E. K. Sanchez2, b, G. Chung2, D. Hansen 2, S. G. Mueller2, and M. J. Loboda2 1 Department of Materials Science and Engineering, Stony Brook University, Stony Brook, NY, USA 11794-2275 2 Dow Corning Compound Semiconductor Solutions, Midland, Michigan, USA 48686-0994 a [email protected], [email protected] ABSTRACT Synchrotron topography studies are presented of the behavior of growth dislocations and deformation-induced dislocations in 4H-SiC single crystals. The growth dislocations include those in threading orientation with line directions approximately along c with Burgers vectors of a, c, and na+mc (where n and m are integers ) while the deformation-induced dislocations include those with line directions confined to the basal plane with Burgers vectors of a and Shockley partial dislocations with Burgers vectors of 1/3 as well as those with line directions in the {1-100} prismatic planes with Burgers vectors of a. Processes leading to the nucleation of the growth dislocations are discussed as well as their deflection onto the basal plane during crystal growth in a reversible process. This latter process can lead to the conversion of segments of the deflected growth dislocations into deformation induced dislocations. In some cases this can lead to dislocation multiplication via the Hopping Frank-Read source mechanism and in others to the motion of single Shockley partial dislocations leading to Shockley stacking fault expansion. Studies are also presented of interactions between threading growth dislocations with c-component of Burger’s vector facilitated by climb processes which are mediated by interactions with non-equilibrium concentrations of vacancies. This can lead to reactions whereby complete or partial dislocation Burgers vector annihilation occurs. INTRODUCTION Threading growth dislocations with line directions approximately parallel to the c-axis in [0001], PVT-grown SiC single crystals have been the subject of many studies over the past two decades, as have basal plane dislocations which are produced through deformations processes [1]. Regarding the growth dislocations, the most prominent of these, c-axis screw dislocations have attracted most attention. These dislocations are found to exist with Burgers vectors of nc, where n is an integer. For 6H-SiC, those with n> 2 have hollow cores while in 4H the same is true for those with n>3 [2]. Such hollow core screw dislocations are referred to as “micropipes.” Detailed studies of the correlation between Burgers vector and hollow core diameter confirmed satisfactory compliance with Frank’s theory of hollow core dislocations [3]. In the meantime, detailed transmission electron microscopy work carried out by Strunk [4] suggested that threading, hollow-core dislocations possessing an a-component to their Burgers vectors also exist in SiC. Indeed, the lack of extinction of Synchrotr
