Enhancement-Mode GaN MOS-HEMTs With Recess-Free Barrier Engineering and High-k ZrO2 Gate Dielectric

Enhancement-mode GaN MOS-HEMTs with a uniform threshold voltage (V-th similar to 2.2 +/- 0.25 V at I-D = 1 mu A/mm) have been achieved by a recess-free barrier engineering technique in conjunction with a high-k gate dielectric. The design includes an ultrathin (similar to 6 nm) Al0.2Ga0.8N barrier preserving the two dimensional electron gas (2DEG) mobility underneath the gate and a selective area barrier regrowth to restore the 2DEG at the access regions. A high-k ZrO2 gate dielectric was employed to enhance the gate control over the channel. The common issue of recess-induced damage was mitigated. The high-quality gate stack results not only in a highly uniform and large V-th, but also small hysteresis, minimal gate lag, low on-resistance, and high output current in the E-MOS-HEMTs.