Regensburg 2004 – wissenschaftliches Programm

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HL: Halbleiterphysik

HL 52: SiC II

HL 52.3: Vortrag

Freitag, 12. März 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 D_IT 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.