Publications

Impact of the Al mole fraction in the bulk- and surface-state induced instability of AlGaN/GaN HEMTs

DasGupta, S.; Sun, M.; Armstrong, Andrew A.; Kaplar, Robert K.; Marinella, M.; Stanley, James B.; Smith, Mark A.; Atcitty, Stanley A.; Palacios, T.

Charge trapping and slow (10 s to > 1000 s) detrapping in AlGaN/GaN HEMTs designed for high breakdown voltage (> 1500 V) are studied to identify the impact of Al molefraction and passivation on trapping. Two different trapping components, TG1 (E a = 0.62 eV) and TG2 (with negligible temperature dependence) in AlGaN dominate under gale bias stress in the off-state. Al 0.15Ga 0.85N shows much more vulnerability to trapping under gate stress in the absence of passivation than does AlGaN with a higher Al mole fraction. Under large drain bias, trapping is dominated by a much deeper trap TD. Detrapping under illumination by monochromatic light shows TD to have E a ≈ 1.65 eV in Al 0.26Ga 0.74N and E a ≈ 1.85 eV in Al 0.15Ga 0.85N. This is consistent with a transition from a deep state (E c - 2.0 eV) in the AlGaN barrier to the 2DEG. © 2012 Materials Research Society.