Effects of the stepped sidewall morphology on the ON-state performance for vertical GaN trench-gate MOSFETs

Vertical GaN trench-gate MOSFETs with similar to 130 nm stepped sidewalls in the p-GaN channel layer are studied and two significant influences have been observed compared to the devices with smooth sidewalls. The first effect is the degraded channel mobility of 14.6 cm(2) (V center dot s)(-1) to 4.5 cm(2) (V center dot s)(-1) which can be attributed to the increased probability of surface acoustic phonons scattering under inversion conditions. Another impact is that only when a drain voltage (V (DS)) is applied over 30 V can the devices switch on. It can be speculated that the stepped sidewall has a horizontal channel and the transverse electric field is inadequate to drive the electrons at low V (DS). According to the investigation, when devices need to be switched at a high V (DS), the stepped sidewall morphology should be taken into consideration.

Automated summary

Vertical GaN trench-gate MOSFETs with stepped sidewalls have been studied and compared to devices with smooth sidewalls. The research observed two significant effects: decreased channel mobility and the requirement of a drain voltage over 30V to switch on.