Ultrathin Body InAlN/GaN HEMTs for High-Temperature (600 $^{\circ} {\rm C}$ ) Electronics

Lattice matched 0.25- $\mu{\rm m}$ gatelength InAlN/GaN high electron mobility transistors are realized in an ultrathin body mesa technology (50-nm AlN nucleation layer/50-nm GaN buffer) on sapphire. At room temperature, the maximum output current density is ${\rm I}_{\rm DS}=0.4~{\rm A}/{\rm mm}$ , the threshold voltage $V_{\rm th}=-1.4~{\rm V}$ with an associated subthreshold voltage swing of 73 mV/dec and a leakage current ${\approx }{\rm 1}~{\rm pA}$ (for ${\rm W}_{G}=50~\mu{\rm m}$ ) and thus a current on/off ratio of $10^{10}$ . At 600 $^{\circ}{\rm C}$ , the maximum drain current, threshold voltage, and transconductance are nearly unchanged. The current on/off ratio is still approximately $10^{6}$ . First 1-MHz class A measurements with ${\pm}{\rm 2.0}~{\rm V}$ peak-to-peak signal amplitude have resulted in 109-mW/mm output power at $V_{\rm DS}=8.75~{\rm V}$ .