Breakdown walkout in pseudomorphic HEMT's

In this work we show for the first time evidence of gate-drain breakdown walkout due to hot electrons in pseudomorphic AlGaAs-InGaAs-GaAs HEMTs (PHEMTs). Experiments performed on passivated commercial PHEMTs show that hot electron stress cycles induce a large and permanent increase of the gate-drain breakdown voltage. Three-terminal and two-terminal stress conditions are compared, the former producing a much larger walkout due to hot electrons flowing in the channel. Experimental results indicate that a build-up of negative charge in the region between gate and drain is responsible for the breakdown walkout, due to a local widening of the depletion region and a reduction of the peak electric field.