High power EBS diode studies

Recent studies of large area EBS diodes for use in a 1 kW 500 MHz CW application are given. Power dissipation of 55 watts CW on a 4 mm²diode has been obtained in excess of 1000 hours with no degradation in reverse voltage characteristics. At higher diode dissipation, current runaway was observed, and this was shown to be a function of the power dissipated in the diode, independent of diode voltage and current over a 100% change in diode voltage and current. The maximum diode dissipation has been related to voids in the braze to the heat sink. Diodes with void-free bonds have shown dissipation levels in excess of 100 watts CW but were limited by degassing problems in the tube. Failure with some void-free bonded EBS diodes was related to breakdown of small ( µm) high conductive regions of the diodes observed with a Scanning Electron Microscope. Auger surface analysis has traced this to a possible residual phosphorus contamination on the top p layer due to removal of excess Al metallization during fabrication.