Tungsten-Gated GaN/AlGaN p-FET With Imax > 120 mA/mm on GaN-on-Si

This letter demonstrates Tungsten (W)-gated p-channel GaN/AlGaN heterostructure field effect transistors on a GaN-on-Si wafer grown by metal organic chemical vapor deposition (MOCVD). The choice of W as the gate metal over the more commonly used Mo induces larger turn-on voltage and lower gate leakage current. An annealing step at 500 degrees C in N-2 ambient was introduced to heal the damage introduced during the gate recess step which resulted in lower channel resistance. Long-channel W-gated p-FETs with L-SD = 5.5 mu m and L-G = 1.5 mu m exhibits an I-ON approximate to 25 mA/mm, I-ON/I-OFF > 10(3). A scaled transistor of dimensions L-SD = 1.2 mu m and L-G = 100 nm demonstrates an I-ON approximate to 125 mA/mm, I-ON/I-OFF approximate to 10(4), and R-ON = 170 Omega. mm.