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

Lattice matched 0.25-μm 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 I
_DS
=0.4A/mm, the threshold voltage V
_th
=-1.4 V with an associated subthreshold voltage swing of 73 mV/dec and a leakage current ≈ 1 pA (for W
_G
=50 μm) and thus a current on/off ratio of 10
¹⁰
. At 600°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 ±2.0 V peak-to-peak signal amplitude have resulted in 109-mW/mm output power at V
_DS
=8.75 V.