Thin-Body N-Face GaN Transistor Fabricated by Direct Wafer Bonding

This letter presents a method to fabricate thin-body N-face GaN-on-insulator-on-Si (100) wafers. These new wafers are promising to increase the carrier confinement and reduce the contact resistance in AlGaN/GaN high electron mobility transistors (HEMTs). In the reported technology, a Ga-face AlGaN/GaN epilayer grown on Si (111) is transferred to a Si (100) wafer by direct wafer bonding and thinned down by selective dry etch to the device active layers. A GaN channel thickness as thin as 20 nm is obtained with the use of AlGaN etch-stop layers. Excellent transport characteristics are obtained in the fabricated thin-body N-face AlGaN/GaN structures, with a sheet resistance of 430 Ω/sq, an electron mobility of 1700 cm²/V · s, and a 2-D electron gas concentration of 9 × 10¹² cm^-2. HEMTs fabricated on these N-face thin-body epilayers shows excellent current-voltage characteristics and great potential for high-frequency applications.