On the Way to the Silicon Carbide IMPATT

An analysis of current situation in silicon carbide R&D shows that it is most real to fabricate SiC IMPATT diode on an epitaxial pn structure grown on the (0001)Si face of 6H-SiC crystal. The operating frequency of this diode will be in the range 90-250 GHz. We calculated numericallydynamic characteristics of the SiC IMPATT diode for pulse mode of operation at the frequency 140 GHz. Results show that the diode conductivity is negative in a wide range of reverse current density (25 - 220 kA/cm
²
). The maximum microwave power generation efficiency of 6% has been calculated for current density of 90 kA/cm
²
and specific input power of 10 MM/cm
²
. Experiments have been done on 6H-SiC pn structures grown by liquid phase epitaxy (LPE). Fabricated diodes revealed avalanche voltages V
b
from 30 to 200 V. A pulse avalanche current was passed through the diodes. The avalanche current density, J
o
, of 60 kA/cm
²
and the specific dissipated power, P
in
, of 9 MW/cm
²
were reached at 60 ns current pulse length. A temperature coefficient of V
b
(ß=V
^-1
dV/dT) was measured at high avalanche current density. For the first time, SiC varactor operated at 150 GHz has been fabricated.