Semi-analytical analysis for optimization of 0.1-μm InGaAs-channel MODFETs with emphasis on on-state breakdown and reliability

We have measured and analyzed the bias limitations of our 0.1-μm In₅₃Ga₄₇As-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_DS^(on) , and thus limits the operating regime. The modeling predicts the shape of BV_DS^(on) vs. I_D and shows that the off-state breakdown voltage is irrelevant for practical load-lines. BV_DS^(on)(I_D) deviates markedly from a constant power locus. In fact, it tends to have a flat minimum BV_DS ^(on,min) (corresponding to maximum impact ionization current) near the I_D of maximum transconductance. BV_DS ^(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_DS^(on,min) with its associated I_D, in contrast to the non-constant-power locus of BV_DS^(on)(I_D) The model predicts both trends well