Low frequency noise in 4H silicon carbide

The bulk low frequency noise has been investigated in the 4H silicon carbide polytype. In the temperature range of 300-550 K the noise spectral density S is proportional to f(-1.5), where f is the measurement frequency. A very low noise level has been observed for the bulk noise. At 300 K, the Hooge constant alpha is as small as (2-4)X10(-6) at f=20 Hz and alpha less than or equal to 5X10(-7) at f=1300 Hz. At T greater than or equal to 600 K, the generation-recombination noise of a local level makes the main contribution into the total low frequency noise. The electron capture cross section sigma of this level depends very strongly on temperature. In the temperature range of 620-700 K, the temperature dependence of sigma can be expressed as sigma similar to exp(-E(1)/kT), with an activation energy E(1) as high as 2.7 eV. (C) 1997 American Institute of Physics.