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 AlN barriers is favorable for scaling by the suppression of short-channel effects. Ohmic contacts are realized with MBE-regrown heavily Si-doped
$\hbox{n}^{+}$
GaN. For long-channel devices, a saturation drain current of
$\sim$
0.7 A/mm at
$V_{\rm GS} = +\hbox{3}\ \hbox{V}$
and a peak extrinsic transconductance of
$ \sim$
160 mS/mm around
$V_{\rm GS} = +\hbox{1}\ \hbox{V}$
are measured at
$V_{\rm DS} = +\hbox{10}\ \hbox{V}$
. 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.