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GaAs FET's with a flicker-noise corner below 1 MHz

GaAs MESFET's with significantly reduced low-frequency noise are demonstrated through application of an understanding that the dominant noise source is generation-recombination (g-r) noise from deep level traps in the gate and backside depletion layers. A 1/f noise spectrum measured from 100 Hz to 10 MHz is modeled as the sum of Lorentzian noise spectra from a few traps subject to the temperature distribution inherent in a GaAs MESFET. The noise associated with a single mid-bandgap trapping level does not appear as an ideal Lorentzian, but rather as 1/f over nearly a decade frequency range by virtue of a time constant that is a strong function of temperature ( exp[Ea/ kT]) and an estimated temperature distribution of 22°C across the active region. The major g-r trap was characterized as having an activation energy of 0.75 eV. By reducing the g-r noise, flicker noise was decreased by more than 15 dB compared to our conventional GaAs MESFET's and the noise corner was reduced to less than 1 MHz from a typical 40 MHz. This significant reduction was achieved by using MBE layers designed to have lower trap concentrations and high channel doping. These results are within 10 dB of the estimated 1/f noise limit due to the quantum mechanics of carrier scattering [5], [14].