Stephan Schwaiger

Charge trapping in gate-drain access region of AlGaN/GaN MIS-HEMTs after drain stress

In this paper we investigate the drain stress behavior and charge trapping phenomena of GaN-based high electron mobility transistors (HEMTs). We fabricated GaN-on-Si MIS-HEMTs with different dielectric stacks in the gate and gate drain access region and performed interface characterization and stress measurements for slow traps analysis. Our results show a high dependency of the on-resistance increase on interfaces in the gate-drain access region. The dielectric interfaces near the channel play a significant role for long term high voltage stress and regeneration of the device.

Poly-silicon CMOS compatible gate module for AlGaN/GaN-on-silicon MIS-HEMTs for power electronics applications

In this paper we present a new poly-silicon gate process for AlGaN/GaN MIS-HEMT power transistors. Using a complete metal-free front-end processing of the gate module the process is fully CMOS compatible. Additionally, the gate reliability can be significantly increased. We used a three-step LPCVD SiN passivation fully enclosing the gate electrode made of polycrystalline silicon. As gate dielectrics LPCVD deposited SiN are used with a thickness of 20 nm and 120 nm. We compared these devices with MIS-HEMTs using Al as gate electrode. Constant current measurements have been performed that show with QBD, poiy, 20 nm = 714 C/cm2 and a MTTF0.5A/cm2 = 1293s significant higher charge pumping capability through the gate for the poly-Si gated devices compared to conventional metal gates.

Trench-MOSFETs on 4H-SiC

This paper introduces n-channel normally-off Trench-MOSFETs on 4H-SiC featuring a blocking voltage of 600 V and 1200 V. The Trench-MOSFETs exhibit a specific room temperature on-state resistance RDS,on of 1.5 mΩ cm² and 2.7 mΩ cm², respectively. It is shown that a further reduction of the RDS,on by approximately 25 % can be achieved using square-shaped or hexagonal unit cells instead of stripe-shaped unit cells. The Trench-MOSFET switching characteristics using a double pulse setup with a switching current Isw of 100 A and a switching voltage Vsw of 450 V is presented and discussed. The short turn-off and turn-on times in the range of several ten nanoseconds yield large maximum disw/dt and dvsw/dt values, which enable highly efficient power conversion with low switching losses.