High Power Density Scaln-Based Heterostructure Fets For Mm-Wave Applications

We report on recent progress on the development of Scandium Aluminum Nitride (ScAlN) based heterostructure field effect transistors ( HFETs). We are leveraging the enhanced polarization properties of ScAlN lattice-matched to Gallium Nitride (GaN) to produce heterostructures that support very large carrier densities (> 3.0x10(13) /cm(2)). We have successfully grown device-quality ScAlN/GaN heterostructures by molecular beam epitaxy (MBE). Using these wafers we have fabricated low resistance contacts for ScAlN barrier HFETs and demonstrated transistors which simultaneously achieve high current density (> 3 A/mm), large breakdown voltage (> 60 V), and good mm-wave small signal gain (> 13 dB at 30 GHz). The high current density coupled with the large breakdown field strength of GaN enables both current and voltage scaling of ScAlN/GaN HFETs and enables design of transistors that overcome the Bode-Fano bandwidth limitations.