AlGaN/GaN metal-insulator-semiconductor high electron mobility transistors (MISHEMTs) using plasma deposited BN as gate dielectric

AlGaN/GaN metal-insulator-semiconductor high electron mobility transistors (MISHEMTs) were fabricated on Si substrates with a 10nm boron nitride (BN) layer as a gate dielectric deposited by electron cyclotron resonance microwave plasma chemical vapor deposition. The material characterization of the BN/GaN interface was investigated by X-ray photoelectric spectroscopy (XPS) and UV photoelectron spectroscopy. The BN bandgap from the B1s XPS energy loss is similar to 5eV consistent with sp(2) bonding. The MISHEMTs exhibit a low off-state current of 1x10(-8)mA/mm, a high on/off current ratio of 10(9), a threshold voltage of -2.76V, a maximum transconductance of 32 mS/mm at a gate voltage of -2.1V and a drain voltage of 1V, a subthreshold swing of 69.1mV/dec, and an on-resistance of 12.75 Omega.mm. The interface state density (D-it) is estimated to be less than 8.49x10(11)cm(-2)eV(-1). Gate leakage current mechanisms were investigated by temperature-dependent current-voltage measurements from 300K to 500K. The maximum breakdown electric field is no less than 8.4MV/cm. Poole-Frenkel emission and Fowler-Nordheim tunneling are indicated as the dominant mechanisms of the gate leakage through the BN gate dielectric at low and high electric fields, respectively.