Fabrication and testing of 4H-SiC IMPATT diodes with p(+)-n-n(+) doping profile is described. The diodes produced a pulsed power of about 300 mW in a frequency range of (8.2-12.4 GHz). Diode microwave characteristics are analyzed and compared with known experimental and theoretical data about high field carrier transport along the c-axis in 4H-SiC.