The improvement of breakdown-voltage (¿2000 V) in GaN based HFETs by using double polarization junctions

A novel AlGaN/GaN Super Heterojunction Field Effect Transistors (super HFET) with dual-polarization junction (DPJ) on the back-barrier layer and its working mechanism is studied. DPJ AlGaN/GaN super HEMT has two polarization junctions with an interval of 1 μm composed of a p-type GaN cap layer and an undoped GaN cap layer, which contact with the gate. In the high voltage blocking state, the two reverse p–n junctions introduced by the polarization junction will effectively modulate the surface electric field and the volume electric field. In addition, this structure suppresses the leakage current of the buffer and leads to higher breakdown voltage. The TCAD simulation results show that at the same gate–drain length of 20 μm, the breakdown voltage of the DPJ structure can be increased from about 1100 V to above 2100 V with an on-resistance of 12.86 Ωmm, slightly higher than that of conventional super HFET. The FOM of DPJ super HFET is up to 1.32 × 109 V2Ω−1cm−2. It shows a better tradeoff relationship between on-resistance and breakdown voltage.