Low-noise behavior of InGaAs quantum-well-structured modulation-doped FET´s from 10-2to 108Hz

Equivalent gate noise voltage spectra of 1-µm gate-length modulation-doped FET\´s with pseudomorphic InGaAs quantum-well structure have been measured for the frequency range of 0.01 Hz to 100 MHz and compared with the noise spectra of conventional AlGaAs/ GaAs MODFET\´s and GaAs MESFET\´s. The prominent generation-recombination (g-r) noise bulge commonly observed in the vicinity of 10 kHz in conventional MODFET\´s at 300 K does not appear in the case of the new InGaAs quantum-well MODFET. Instead, its noise spectra indicate the presence of low-intensity multiple g-r noise components superimposed on a reduced noise. The LF noise intensity in the new device appears to be the lowest among those we have observed in any MODFET or MESFET. The noise spectra at 82 K in the new device represent nearly true noise. This unusual low-noise behavior of the new structure suggests the effectiveness of electron confinement in the quantum well that significantly reduces electron trapping in the n-AlGaAs, and thus eliminates the g-r noise bulge observed in conventional MODFET\´s.