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 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex Notation="TeX">n⁺</tex></formula> GaN. For long-channel devices, a saturation drain current of <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">~</tex></formula> 0.7 A/mm at <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">VGS = +3\ V</tex></formula> and a peak extrinsic transconductance of <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">~</tex></formula> 160 mS/mm around <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">VGS = +1\ V</tex> </formula> are measured at <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">VDS = +10\ V</tex></formula> . No hysteresis is observed in the <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">C</tex></formula> – <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">V</tex></formula> 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.