Scaling of E-mode power GaN-HEMTs for low voltage/low Ron applications: Implications on robustness

We analyze the impact of scaling on the off-state, three-terminal, lateral breakdown of 100 V E-mode p-GaN/AlGaN/GaN HEMTs for low-voltage/low on-resistance applications. To this aim, we compared device structures with different SiO2 dielectric thickness below the field plate, and varying gate-to-drain spacing and field-plate dimensions. The results indicate that: a) the breakdown voltage depends on the geometry and on the thickness of the dielectric under the field plate (tSiO2); b) scaling the dielectric thickness increases the sensitivity of breakdown voltage to the gate-drain distance, while preserving device robustness (breakdown voltages above 150 V for a 100 V technology); c) for the devices with thinner dielectric, breakdown voltage scales linearly with gate drain distance, and with field plate length. A further analysis of the data reveals that the critical parameter in terms of reliability is the distance between the field-plate edge and the drain contact; d) scaling of the dielectric thickness does not enhance charge trapping phenomena. In summary, the results provide guidelines for scaling GaN HEMT device dimensions, while preserving reliability and immunity to charge trapping phenomena.