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HL: Halbleiterphysik
HL 52: SiC II
HL 52.3: Talk
Friday, March 12, 2004, 12:45–13:00, H17
Low Density of Interface States in 4H-SiC MOS Capacitors Generated by Nitrogen Implantation — •Florin Ciobanu1, Gerhard Pensl1, Valeri Afanas’ev2, and Günter Wagner3 — 1Lehrstuhl für Angewandte Physik — 2Department of Physics, University of Leuven, Belgium — 3Institut für Kristallzüchtung, Berlin
Nitrogen (N)-doped 4H-SiC epilayers (thickness = 8µm, [N] = 2.2·1016cm−3) were, in addition, implanted with N at concentrations varying between 1·1017cm−3 and 3·1019cm−3 (Gaussian profile with maximum located 30nm apart from the wafer surface). MOS capacitors were fabricated on the N-implanted surface by nominally dry oxidation at 1120∘C for 24 h (oxide thickness = 110nm) followed by a post-oxidation anneal at the same temperature in Ar for 60 min. High-frequency conductance measurements reveal an interface state density DIT in the low 1010eV−1cm−2 - range close to the conduction band edge. This value is about 3 orders of magnitude lower than corresponding values for standard-processed 4H-SiC MOS capacitors. However, the N implantation causes a negative flatband shift of the C-V characteristics, which probably originates from a fixed charge at the interface (≈1012 elementary charges/cm2). The effect of the implanted N concentration on the density of interface states and on the flatband shift is investigated and discussed.