Experimental determination of electron drift velocity in 4H-SiC p+-n-n+ avalanche diodes

4H-SiC p(+)-n-n(+) diodes of low series resistivity (<1 x 10(-4) Omega.cm(2)) were fabricated and packaged. The diodes exhibited homogeneous avalanche breakdown at voltages U-b =250-270 V according to the doping level of the n layer. The temperature coefficient of the breakdown voltage was measured to be 2.6 x 10(-4) K-1 in the temperature range 300 to 573 K. These diodes were capable to dissipate a pulsed power density of 3.7 MW/cm(2) under avalanche current conditions. The transient thermal resistance of the diode was measured to be 0.6 K/W for a 100-ns pulse width. An experimental determination of the electron saturated drift velocity along the c-axis in 4H-SiC was performed for the first time. It was estimated to be 0.8 x 10(7) cm/s at room temperature and 0.75 x 10(7) cm/s at approximately 460 K.