Demonstration of undoped quaternary AlInGaN/GaN heterostructure field-effect transistor on sapphire substrate

Undoped AlInGaN/GaN heterostructure field-effect transistors (HFETs) have been demonstrated on sapphire substrate. The maximum drain current of 758 mA/mm and extrinsic transconductance of 123 mS/mm were obtained from the device with 2 mu m gate length and 15 mu m gate width. Such performance was comparable to that of a conventional modulation-doped (MOD) AlGaN/GaN HFET fabricated at same the condition. In spite of the high-density two-dimentional electron gas formed at the heterointerface, the AlInGaN/GaN HFET structure showed relatively low Hall mobility (689 cm(2)/V s at 300 K), which was due to the high concentration background doping in the undoped AlInGaN barrier region. Encouragingly, both the gate leakage current and drain current collapse showed lower values than that of the MOD-AlGaN/GaN HFET, which implied the potential application of quaternary AlInGaN to high-power and high-frequency devices. (c) 2005 American Institute of Physics.