Polarization Engineered Design for Normally-Off, Higher Drain Current and Higher Breakdown Voltage Gan-Based MOS-HEMT

In this work we propose a novel design for an enhancement-mode gallium nitride (GaN) high-electron-mobility transistor (HEMT) that achieves normally off operation along with increased drive current and improved breakdown voltage. The device uses an undoped aluminum nitride (AlN) buffer layer to boost breakdown strength. By etching the AlN buffer into a fin-like shape under the gate, a two-dimensional hole gas (2DHG) forms at the GaN/AlN interface. This 2DHG locally depletes the two-dimensional electron gas (2DEG) under the gate, thereby converting the transistor to enhancement-mode. Silvaco ATLAS Technology Computer-Aided Design (TCAD) simulations have been performed and calibrated with experimental data, to validate the effectiveness of the proposed structure. The results demonstrate a positive threshold voltage of about +2.3 V, ∼6× increase in maximum drain current, and ∼2.4× increase in breakdown voltage compared to a conventional PE-HEMT. The influence of key design parameters (AlN fin depth, length, and polarization scaling) on the device performance is analyzed in detail. An AC analysis was also conducted, revealing that the proposed device achieves a 1.4× improvement in cutoff frequency (<i>f</i> _T) and a 1.2× increase in maximum oscillation frequency (<i>f</i> _max) compared to the conventional PE-HEMT. The proposed GaN MOS-HEMT shows promising features for next-generation high-power and RF electronics which offers a reliable normally off operation with enhanced current drive and high voltage capability.