Formation of carbon vacancy in 4H silicon carbide during high-temperature processing Available to Purchase

As-grown and pre-oxidized silicon carbide (SiC) samples of polytype 4H have been annealed at temperatures up to 1950 °C for 10 min duration using inductive heating, or at 2000 °C for 30 s using microwave heating. The samples consisted of a n-type high-purity epitaxial layer grown on 4° off-axis ⟨0001⟩ n⁺-substrate and the evolution of the carbon vacancy (V_C) concentration in the epitaxial layer was monitored by deep level transient spectroscopy via the characteristic Z_1/2 peak. Z_1/2 appears at ∼0.7 eV below the conduction band edge and arises from the doubly negative charge state of V_C. The concentration of V_C increases strongly after treatment at temperatures ≥ 1600 °C and it reaches almost 10¹⁵ cm⁻³ after the inductive heating at 1950 °C. A formation enthalpy of ∼5.0 eV is deduced for V_C, in close agreement with recent theoretical predictions in the literature, and the entropy factor is found to be ∼5 $k$ (⁠$k$ denotes Boltzmann's constant). The latter value indicates substantial lattice relaxation around V_C, consistent with V_C being a negative-U system exhibiting considerable Jahn-Teller distortion. The microwave heated samples show evidence of non-equilibrium conditions due to the short duration used and display a lower content of V_C than the inductively heated ones. Finally, concentration-versus-depth profiles of V_C favour formation in the “bulk” of the epitaxial layer as the prevailing process and not a Schottky type process at the surface.