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Analysis of threshold voltage instability in AlGaN/GaN MISHEMTs by forward gate voltage stress pulses
Author(s) -
Winzer Annett,
Schuster Martin,
Hentschel Rico,
Ocker Johannes,
Merkel Ulrich,
Jahn Andreas,
Wachowiak Andre,
Mikolajick Thomas
Publication year - 2016
Publication title -
physica status solidi (a)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.532
H-Index - 104
eISSN - 1862-6319
pISSN - 1862-6300
DOI - 10.1002/pssa.201532756
Subject(s) - materials science , threshold voltage , optoelectronics , gate dielectric , stress (linguistics) , negative bias temperature instability , gate oxide , voltage , high κ dielectric , capacitance , dielectric , electrical engineering , transistor , electrode , physics , linguistics , philosophy , engineering , quantum mechanics
We report on the investigation of the V th drift behaviour of AlGaN/GaN MISHEMTs upon forward gate voltage stress in dependence of stress bias and stress time. The pulsed measurements allow for the evaluation of the operational regime for optimum device efficiency. We compared the effect of two different high‐ κ gate dielectric materials with similar equivalent oxide thickness ϵ 0 ϵ r / t high‐κ on the V th instability in order to separate the influence of the heterojunction design and the high‐ κ /GaN‐cap interface from the bulk high‐ κ . The matched gate capacitance coupling of the studied Al 2 O 3 and HfO 2 gate dielectric results in an nearly identical critical forward gate voltage, where the AlGaN barrier potential is lowered and severe threshold voltage shift (Δ V th ) into the positive voltage direction is induced. Beyond this critical forward voltage, detailed time‐dependent stress pulse measurements from 1 µs to 1000 s revealed an immediate electron injection and trapping at the oxide/GaN interface for stress pulses with t stress ≥ 1 µs. The presented results of V th drift analysis demonstrate the limits of the maximum tolerable forward gate voltage of the investigated Al 2 O 3 and HfO 2 MISHEMTs, although the excellent low‐leakage currents of the insulated gate would imply a potentially higher gate‐overdrive.