AlGaN/GaN HEMTs on 4-Inch Silicon Substrates in the Presence of 2.7-µm -Thick Epilayers with the Maximum Off-State Breakdown Voltage of 500 V

We report on the high breakdown performance of AlGaN/GaN high electron mobility transistors (HEMTs) grown on 4-inch silicon substrates. The HEMT structure including three Al-content step-graded AlGaN transition layers has a total thickness of 2.7 μm. The HEMT with a gate width W_G of 300 μm acquires a maximum off-state breakdown voltage (BV) of 550 V and a maximum drain current of 527 mA/mm at a gate voltage of 2 V. It is found that BV is improved with the increase of gate-drain distance L_GD until it exceeds 8 μm and then BV is tended to saturation. While the maximum drain current drops continuously with the increase of L_GD. The HEMT with a W_G of 3 mm and a L_GD of 8 μm obtains an off-state BV of 500 V. Its maximum leakage current is just 13 μA when the drain voltage is below 400 V. The device exhibits a maximum output current of 1 A with a maximum transconductance of 242 mS.