75 angstrom GaN channel modulation doped field effect transistors

A III-V nitride modulation doped field effect transistor (MODFET) layer structure grown by organometallic vapor phase epitaxy (OMVPE) on a sapphire substrate was employed for transistor fabrication, The MODFET layer structure contained a 75 Angstrom GaN channel, 50 Angstrom A(0.16)Ga(0.84)N spacer, 20 Angstrom Si doped charge supply layer, 130 Angstrom Al0.16Ga0.84N barrier, and 60 Angstrom Al0.06Ga0.94N cap layer. The thin channel (75 Angstrom) was chosen to improve the carrier confinement in the channel. The fabricated MODFET's had 0.25 mu m long gates, and utilized a Au-Si alloy Ohmic metal and a Ti/Pd/Au gate metal. The measured transconductance was 40 mS/mm. From the microwave measurements on devices with 0.25 mu m long gates, f(t) and f(max) were determined to be 21.4 and 77.5 GHz, respectively. (C) 1996 American Institute of Physics.