OBSERVATION OF HIGH-FREQUENCY HIGH-FIELD INSTABILITY IN GAAS/INGAAS/ALGAAS DH-MODFETS AT K-BAND

The authors report the observation of high-field instability at room temperature with oscillation frequency as high as 24 GHz in GaAs/InGaAs/AlGaAs double-heterojunction-MODFETs (DH-MODFETs) of 1. 2 mu m gate length. Negative drain differential resistance was also observed in these devices under various forward gate biases. The nature of this instability is believed to be caused by the efficient removal of the real-space transferred hot two-dimensional electrons in the AlGaAs layer through the forward-biased Schottky gate. A tuned oscillator, with a fundamental oscillation frequency as high as 19. 68 GHz, has also been demonstrated at a gate bias of 1. 3 V.