Characterisation and modelling of parasitic effects and failure mechanisms in AlGaN/GaN HEMTs (original) (raw)
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Trapping related degradation effects in AlGaN/GaN HEMT
2010
Reliability in GaN based devices still motivates numerous studies because the involved degradation mechanisms are different from that in III-V narrow bandgap devices. Direct investigations on high electron mobility transistors (HEMT) are performed with low frequency noise (LFN) measurements and pulsed electrical characterization. Undoped AlGaN/GaN devices grown on silicon substrate are stressed at a junction temperature of 175°C. Gate-lag and drain-lag measurements method have been performed versus different quiescent bias points and under different pulse conditions. This method allows the discrimination of each lag phenomenon as well as the thermal contribution. Thus it is possible to track and model the trapping mechanisms versus bias conditions. This electrical modelling is completed with LFN measurements, which is largely used for reliability investigations.
Electrostatic Mechanisms Responsible for Device Degradation in AlGaN/GaN HEMTs
The World Academy of Research in Science and Engineering
The various factors that are responsible for device degradation are examined. The interplay between Non-Idealities in GaN HEMTs, traps, polarization, Origin of 2DEG, Current Collapse, Virtual gate, is analyzed and quantified. The various factors that helps in getting desired device characteristics regarding performance are studied and methods for achieving their satisfactory values are reviewed.
Reverse bias stressing in AlGaN/GaN high electron mobility transistors (HEMTs) compelled severe degradation of drain current (I DS) whereas gate current (I G) remained largely unaffected. Besides, the response of access region conductivity to pulse drives was found to deteriorate gradually as a result of stress, and an interacting deep level in the form of kink effect was observed. Post degradation, SEM imaging evidenced the field-induced formation of protruding particles, immediately adjacent to the gate electrode. Auger spectroscopy and elemental mapping chemically identified these insulating particles as gallium oxide. Barrier/channel consumption in the form of electrochemical oxidation is thus held responsible for I DS degradation whereas I G degradation is entirely attributed on the presence of passivation layer. SEM micrographs of the (a) tested, and (b) untested finger of a À80 V bias stressed HEMT. (c) Auger spectra from an insulating particle, whereas (d) and (e) are oxygen and gallium elemental maps of the entire frame (c).