Experimental observation of velocity overshoot in n-channel AlGaAs/InGaAs/GaAs enhancement mode MODFETs

Velocity overshoot phenomena in n-channel Al-GaAs/InGaAs/GaAs enhancement mode MODFETs have been investigated for gate lengths ranging from 1 to 0.5 μm. The study is based on Motorola´s established CGaAs/sup TM/ technology. The observed average electron velocity /spl upsi//sub a/spl upsi// under the gate is 1.05, 1.34, 1.48, and 1.71×10/sup 7/ cm/s for a gate length L/sub G/ of 1, 0.7, 0.6, and 0.5 μm, respectively. The presence of velocity overshoot in InGaAs channels is clearly proven with average electron velocities exceeding the steady-state saturation velocity of /spl cong/1×10/sup 7/ cm/s for L/sub G//spl les/0.7 μm, and with the significant increase of /spl upsi//sub a/spl upsi// with shorter gate length.