Traps characterization in Si-doped GaN/AlGaN/GaN HEMT on SiC by means of low frequency techniques

Wide band gap AlGaN/GaN heterostructure offers the potential for high-electron mobility transistors (HEMTs) suitable for high-power and high-temperature operations. Despite the impressive performance already published, both passivated and unpassivated devices suffer from phenomena that was related to the presence or creation of traps, namely “current collapse” and degradation from hot-electrons [3]. In the first part of the evolution of the GaN HEMT technology, many studies were conduced to improve device performances, in particular to achieve high breakdown voltage and high density of the two dimensional electron gas but without take in account the effect of these solutions under real pulsed conditions and under long-term stress. Particularly, many studies reported contradictory data on the role of the passivation in reducing the current collapse [4]. Clearly, for practical application, passivation for electronic devices is inevitable and a correct physical understanding of the dispersion is demanded, even if up to now a complete explanation of the phenomena is lacking. To improve the understanding of the current collapse and hot-electrons effect, many techniques of characterisation were proposed to give evidence of the electron traps.