High Temperature Operation of Al_0.45Ga_0.55N/Al_0.30Ga_0.70N High Electron Mobility Transistors

AlGaN-channel high electron mobility transistors (HEMTs) are among a class of ultra wide-bandgap transistors that have a bandgap greater than ∼3.4 eV, beyond that of GaN and SiC, and are promising candidates for RF and power applications. Long-channel AlxGa1-xN HEMTs with x = 0.3 in the channel have been built and evaluated across the −50°C to +200°C temperature range. Room temperature drain current of 70 mA/mm, absent of gate leakage, and with a modest −1.3 V threshold voltage was measured. A very large Ion/Ioff current ratio, greater than 108 was demonstrated over the entire temperature range, indicating that off-state leakage is below the measurement limit even at 200°C. Combined with near ideal subthreshold slope factor that is just 1.3× higher than the theoretical limit across the temperature range, the excellent leakage properties are an attractive characteristic for high temperature operation.