Breakdown walkout in pseudomorphic HEMTs

In this work we show for the first time evidence of gate-drain breakdown walkout due to hot electrons in pseudoniorphic AlGaAs/InGaAs/GaAs HEMT's (PHEMT's). Experiments performed on passivated commercial PHEMT's show that hot electron stress cycles induce a large and permanent increase of the gate-drain breakdown voltage. Three-terminal and twoterminal stress conditions are compared, the former producing a much larger walkout due to hot electrons Bowing 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.