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

Abstract

4H-SiC p/sup +/-n-n/sup +/ diodes of low series resistivity (<1/spl times/10/sup -4/ /spl Omega//spl middot/cm/sup 2/) were fabricated and packaged. The diodes exhibited homogeneous avalanche breakdown at voltages U/sub 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/spl times/10/sup -4/ k/sup -1/ in the temperature range 300 to 573 K. These diodes were capable of dissipating a pulsed power density of 3.7 MW/cm/sup 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/spl times/10/sup 7/ cm/s at room temperature and 0.75/spl times/10/sup 7/ cm/s at approximately 360 K.