Effect of hydrostatic pressure on the dc characteristics of AlGaN/GaN heterojunction field effect transistors

We report the effect of compressive hydrostatic pressure on the current-voltage characteristics of AlGaN/GaN heterojunction field effect transistors (HFETs) on a sapphire substrate. The drain current increases with hydrostatic pressure and the maximum relative increase occurs when the gate bias is near threshold and drain bias is slightly larger than saturation bias. The increase of the drain current is associated with a pressure induced shift of the threshold voltage by -8.0 mV/kbar that is attributed to an increase of the polarization charge density at the AlGaN/GaN interface due to the piezoelectric effect. The results demonstrate the considerable potential of AlGaN/GaN HFETs for strain sensor applications.