A MICROSCOPIC ANALYSIS OF THE CARRIER-VELOCITY DISTRIBUTION AND THE NOISE IN FET DEVICES

We present a compared microscopic analysis of the transport and noise performances of submicron GaAs MESFET and GaAs/AlGaAs HEMT. The calcul ations are performed using a Monte Carlo modeling including real-space transfer and quantized electrons in the HEMT. We have found a much lo wer drain-current variance in the HEMT that we link to a very sharp ca rrier-velocity distribution at the beginning of the channel and a shor ter average carrier transit time. Moreover, the average carrier transi t time exhibits for both devices a minimum value just at the beginning of the saturation regime.