Origins and characterization of low-frequency noise in GaAs MESFET's grown on InP substrates

An experimental study of the low-frequency noise in GaAs MESFET's grown on InP substrates is reported. The influence of the biases applied to the gate, backgate, and drain in the ohmic region is investigated in order to identify and characterize the 1/f noise origin. We find that this noise can be explained by carrier number fluctuations in the channel and related to trapping phenomena. The traps responsible for this noise are located near the channel-buffer interface. Moreover, the noise behavior exhibits for a well-defined gate voltage, corresponding to the case where the drain current flows near the channel-buffer interface, a GR-type (Lorentzian) noise spectrum emerging from a quite general 1/f noise. This last spectrum corresponds to a single trap level with a density of N/sub T/=10/sup 16/ cm/sup -3/ and a time constant /spl tau/=1.8 ms which may be attributed to crystal defects present in the GaAs layers.