Effect of illumination on the electrical characteristics of AlGaN/GaN FETs

Piezoelectric AlGaN/GaN FETs with high carrier mobility have been fabricate d yielding I-DS = 450 mA/mm and g(m), = 200 mS/mm. Upon turn-on of the devi ce 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 > 2 5 V applied in on-state. The relaxation time tau of this effect is of the o rder of several hundred seconds. From the temperature dependence of t an ac tivation energy Of about 280 meV and a capture cross section of 4.4 x 10(-1 8) cm(2) can be extracted.