Stacking faults which formed during the forward biasing of 4H-SiC p-i-n diodes were identified by using site-specific plan-view transmission electron microscopy and light emission imaging. These stacking faults were bounded by Shockley partial dislocations, and were formed by shear strain rather than by the condensation of vacancies or interstitials. Detailed analysis, using transmission electron microscopic diffraction contrast experiments, revealed stacking faults with leading C-core Shockley partial dislocations as well as with the Si-core partial dislocations observed in the plastic deformation of 4H-SiC at high temperatures. The leading Shockley partials were seen to relieve both tensile and compressive strains during p-i-n diode operation; thus suggesting Structure of Stacking Faults Formed during the Forward Bias of 4H-SiC p-i-n Diodes. M.E.Twigg, R.E.Stahlbush, M.Fatemi, S.D.Arthur, J.B.Fedison, J.B.Tucker, S.Wang: Applied Physics Letters, 2003, 82[15], 2410-2