Ultrathin Body GaN-on-Insulator Quantum Well FETs With Regrown Ohmic Contacts

A technology similar to silicon-on-insulator is highly desirable for III-V electronics to support scaling for future generations. This letter reports the first realization of strained GaN quantum-well transistors embedded in unstrained AlN as the insulator. The molecular beam epitaxy (MBE)-grown heterostructure consisting of an ultrathin GaN channel buried in strain-free AIN barriers is favorable for scaling by the suppression of short-channel effects. Ohmic contacts are realized with MBE-regrown heavily Si-doped n⁺ GaN. For long-channel devices, a saturation drain current of ~0.7 A/mm at V_GS = +3 V and a peak extrinsic transconductance of ~160 mS/mm around V_GS = +1 V are measured at V_DS = +10 V. No hysteresis is observed in the C-V measurement, indicating the high quality of all binary nitride heterostructures. The demonstrated device structure offers a high promise for high-frequency and high-power applications in the future. The strain-free barrier has the potential to enhance the reliability of GaN transistors.