Semi-analytical analysis for optimization of 0.1-/spl mu/m InGaAs-channel MODFETs with emphasis on on-state breakdown and reliability

摘要

We have measured and analyzed the bias limitations of our 0.1-/spl mu/m In/sub 53/Ga/sub 47/As-channel MODFETs. A semi-analytical model allows us to correlate a major degradation mechanism, the increase in drain resistance to impact ionization in the narrow-bandgap channel. We find, as others have, that this mechanism also determines the on-state breakdown voltage BV/sub DS//sup (on)/, and thus limits the operating regime. The modeling predicts the shape of BV/sub DS//sup (on)/ vs. I/sub D/ and shows that the off-state breakdown voltage is irrelevant for practical load-lines. BV/sub DS//sup (on)/(I/sub D/) deviates markedly from a constant power locus. In fact, it tends to have a flat minimum BV/sub DS//sup (on,min)/ (corresponding to maximum impact ionization current) near the I/sub D/ of maximum transconductance. BV/sub DS//sup (on,min)/ becomes the most significant measure of FET breakdown. Most of our device variations have tended to produce a constant-power trade-off of BV/sub DS//sup (on,min)/ with its associated I/sub D/, in contrast to the non-constant-power locus of BV/sub DS//sup (on)/(I/sub D/) The model predicts both trends well.