Regensburg 2007 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 40: SiC
HL 40.1: Vortrag
Donnerstag, 29. März 2007, 12:30–12:45, H15
Space-charge waves in SiC — •Michaela Lemmer1, Mirco Imlau1, Manfred Wöhlecke1, Mikhail Petrov2, and Valeriy Bryksin2 — 1Department of Physics, University of Osnabrück, Germany — 2Ioffe Physico-Technical Institute, St.
The phenomenon of space-charge waves (SCW) is comprehensively
studied in the field of nonlinear optics. SCW are eigenmodes of
spatial-temporal oscillations of a space-charge density appearing
in semi-insulating materials in an external electric field. The
behaviour of low-frequency SCW, like those found in SiC, depends
on the defect structure of the investigated material. As the
defect structure in SiC is a promising scientific topic, we apply
the method of resonant SCW excitation to a 4H-SiC
polytype.
In this case, SCW are excited with an oscillating interference
pattern and an externally applied electric field of 0 < E0 ≤
10 kV/cm. If the frequency of the interference pattern coincides
with the eigenfrequency of the SCW mode, resonant excitation
occurs. Because of a relatively low trap concentration in SiC,
causing the effect of trap saturation, the general theory has to
be modified. With this assumption, all results are found in a good
agreement with the theoretical concept. This allows to determine
important material parameters of 4H-SiC like the product of
mobility and lifetime of the charge carriers µ τ = (7.4
± 0.8) · 10−7 cm2/V, the Maxwell relaxation time
τM = (5.3 ± 0.6) · 10−4 s, and the effective
trap concentration Neff = (5 ± 1) ·
1013 cm−3.
Supported by the Deutsche Forschungsgemeinschaft (DFG, projects
GRK 695 and 436 RUS 17/15/07).