Improved Normally-Off 1200 V GaN-on-Si MOS-HEMT with Novel AlGaN Back Barrier

This paper reports for the first time a novel AlGaN and Mg doped GaN Back Barrier (AlGaN BB and Mg-BB respectively) on fully recessed GaN MOS High Electron Mobility Transistors (MOS-HEMTs) fabricated on 200 mm Si substrates. These BB were introduced to increase and stabilize the transistor threshold voltage $(\mathbf {V}_{\mathbf {T}\mathbf {H }})$ under harsh test conditions. The impact of the Al percentage (Al%) in the AlGaN BB was evaluated, revealing a parasitic transistor that was suppressed with careful optimization of the AlGaN BB properties. Then, the optimized AlGaN BB was compared to the Mg-BB, showing both improved ON state resistance (RON) and $\mathbf {V}_{\mathbf {T}\mathbf {H }} > +1$ V. Dynamic characterizations were carried out as well and demonstrated superior $\mathbf {V}_{\mathbf {T}\mathbf {H }}$ and $\mathbf {R}_{\mathbf {O}\mathbf {N}}$ stability thanks to the novel AlGaN BB. The transistors voltage rating was also studied showing a 1550 V buffer-limited maximum breakdown voltage, fulfilling the specifications for 1200 V applications.