Threshold Voltage Instability in p-GaN Gate AlGaN/GaN HFETs

We investigate the impact of the gate contact on the threshold voltage stability in p-GaN gate AlGaN/GaN heterojunction field-effect transistors with double pulse measurements on the p-GaN gate devices and device simulations. We find that, under gate stress, in the case of high-leakage Schottky cont...

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Bibliographic Details
Published in:IEEE transactions on electron devices 2018-06, Vol.65 (6), p.2454-2460
Main Authors: Sayadi, Luca, Iannaccone, Giuseppe, Sicre, Sebastien, Haberlen, Oliver, Curatola, Gilberto
Format: Article
Language:English
Subjects:
Aluminum gallium nitride
Gate stress
HEMT
hole injection
Logic gates
p-GaN gate
Schottky barriers
Schottky contact
Stress
Threshold voltage
threshold voltage shift
Voltage measurement
Wide band gap semiconductors
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Summary:We investigate the impact of the gate contact on the threshold voltage stability in p-GaN gate AlGaN/GaN heterojunction field-effect transistors with double pulse measurements on the p-GaN gate devices and device simulations. We find that, under gate stress, in the case of high-leakage Schottky contact, a negative threshold voltage shift results from hole accumulation in the p-GaN region. Conversely, in the case of low-leakage Schottky contact, hole depletion in the p-GaN region gives rise to a positive threshold voltage shift. More generally, we show that an imbalance between the hole tunneling current through the Schottky barrier and the thermionic current across the AlGaN barrier results in a variation of the total charge stored in the p-GaN region, which in turn is responsible for the observed threshold voltage shift. Finally, we present a simplified equivalent circuit model for the p-GaN gate module.
ISSN:0018-9383
1557-9646
DOI:10.1109/TED.2018.2828702