New factors affecting HFET stability, 1/f noise, and reliability

We have explored the practical applicability of our recently found stability criterion for HFETs with spontaneous polarization of the gate insulation, to determine in which conditions the criterion is satisfied. In essence, the criterion requires a faster decrease of the spontaneous gate polarization than of the resistivity when temperature increases locally. The instability will be stronger in certain temperature intervals, and will result in degradation and 1/f noise increase. The implications for engineering design for increased device reliability at large positive gate bias and high power dissipation are analyzed. Our criterion and optimization principle also includes the effect of the plasmon-optical phonon resonance effects in the channel, which could even reverse the channel resistance decrease when temperature is raised in the stationary regime.