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Piezoelectric AlGaN/GaN FETs on SiC with high carrier mobility have been fabricated yielding I DS =450 mA/mm and g m =200 mS/mm. In the on-state, under UV-illumination, the devices sustain a drain voltage of V DS =49 V, corresponding to a power dissipation of 26.5 W/mm. On turn-on of the device from the pinch-off state, a significant delay in the drain current build-up is observed. This effect depends on the pinch-off time and the pinch-off voltage and can be removed by either a brief UV-illumination or a V DS >25 V applied in the on-state. The drain current transients are characterized by a relaxation time τ , which is in the order of several hundred seconds. From the temperature dependence of τ , an activation energy of about 280 meV and a capture cross section of 4.4·10 -18 cm 2 were determined. The devices show pronounced persistent photoconductivity (PPC) and the drain current I D is sensitive to illumination.

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Piezoelectric AlGaN/GaN FETs with high carrier mobility have been fabricated yielding I DS 450 mA/mm and g m 200 mS/mm. Upon turn-on of the device from the pinch-off state a significant delay in the drain current build-up is observed. This effect depends on the pinch-off time and the pinch-off voltage and can be removed by either a brief UV-illumination or a V DS b 25 V applied in on-state. The relaxation time t of this effect is of the order of several hundred seconds. From the temperature dependence of t an activation energy of about 280 meV and a capture cross section of 4X4 Â 10 À18 cm 2 can be extracted.