Symmetrical V<sub>TH</sub>/R<sub>ON</sub> Drifts Due to Negative/Positive Gate Stress in p-GaN Power HEMTs
Nicolò Zagni, Marcello Cioni, Maria Eloisa Castagna, Maurizio Moschetti, Ferdinando Iucolano, G. Verzellesi, Alessandro Chini
Abstract
We investigate the drift of threshold voltage (V <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">TH</inf> ) and on-resistance (R <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ON</inf> ) in p-GaN power HEMTs after being submitted to negative/positive gate stress. Negative (Positive) Gate Stress (NGS/PGS) was applied at a gate-to-source bias of |V <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">NGS</inf> | = V <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">PGS</inf> = 6 V up to a cumulative stress time of 8×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> s at room temperature. We found that during NGS both V <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">TH</inf> and R <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ON</inf> increased over stress time, whereas during PGS both parameters decreased and stabilized to the values prior to stress application. This symmetric behavior was maintained after 5 full NGS/PGS stress cycles, indicating the absence of permanent degradation. To further characterize the V <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">TH</inf> and R <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ON</inf> transients, the NGS/PGS stress cycles were repeated at different temperatures (T=30-105 °C). While V <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">TH</inf> exhibited a strong Τ-dependence (E <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">A</inf> ≈ 0.6 eV) during NGS, a negligible variation of the V <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">TH</inf> transients with T was found during PGS (E <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">A</inf> ≈ 0 eV). Instead, R <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ON</inf> transients exhibited approximately the same T-dependence during both NGS and PGS (E <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">A</inf> ≈ 0.3-0.4 eV).