The effects of thermal storage on GaN–HEMT devices grown on SiC substrate have been investigated by DC and pulsed electrical measurements, breakdown measurements (by means of a Transmission Line Pulser, TLP), and optical and electron microscopy. After 3000 h of thermal storage testing at 300 C, only a limited reduction of the DC drain saturation current and of the transconductance peak was observed (20% and 25% decrease, respectively). However, pulsed measurements on aged devices clearly highlight a dramatic current collapse effect that has been attributed to a creation of surface traps in the gate-todrain and gate-to-source access region. On-state breakdown characterization carried out on aged devices did not highlight any noticeable changes with respect to the untreated devices similarly to the DC characterization. Failure analyses have demonstrated that a loss of adhesion of the passivation layer was responsible for the observed trap formation. An improved passivation deposition process was therefore developed, including a surface cleaning procedure aimed at preventing passivation detaching. The devices fabricated using this new procedure do not show any enhancement of trapping effects up to 500 h of thermal stress at 300 C.

Thermal storage effects on AlGaN/GaN HEMT

DANESIN, FRANCESCA;TAZZOLI, AUGUSTO;ZANON, FRANCO;MENEGHESSO, GAUDENZIO;ZANONI, ENRICO;
2008

Abstract

The effects of thermal storage on GaN–HEMT devices grown on SiC substrate have been investigated by DC and pulsed electrical measurements, breakdown measurements (by means of a Transmission Line Pulser, TLP), and optical and electron microscopy. After 3000 h of thermal storage testing at 300 C, only a limited reduction of the DC drain saturation current and of the transconductance peak was observed (20% and 25% decrease, respectively). However, pulsed measurements on aged devices clearly highlight a dramatic current collapse effect that has been attributed to a creation of surface traps in the gate-todrain and gate-to-source access region. On-state breakdown characterization carried out on aged devices did not highlight any noticeable changes with respect to the untreated devices similarly to the DC characterization. Failure analyses have demonstrated that a loss of adhesion of the passivation layer was responsible for the observed trap formation. An improved passivation deposition process was therefore developed, including a surface cleaning procedure aimed at preventing passivation detaching. The devices fabricated using this new procedure do not show any enhancement of trapping effects up to 500 h of thermal stress at 300 C.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11577/2267511
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