LOW-FREQUENCY NOISE SOURCES IN INALAS INGAAS MODFETS/

Detailed analysis of the 1/f low-frequency noise (LFN) in In0.52Al0.48 As/InGaAs MODFET structures is performed, for low drain bias (below pi nch-off voltage), in order to identify the physical origin and the loc ation of the noise sources responsible for drain current fluctuations in the frequency range 0.1 Hz-10(5) Hz, Experimental data were analyze d with the support of a general modeling of the 1/f LFN induced by tra ps distributed within the different layers and interfaces which consti tute the heterostructures, Comparative noise measurements are performe d on a variety of structures with different barrier (InAlAs, InP) and different channel (InGaAs lattice matched to InP, strained InGaAs, InP ) materials, It is concluded that the dominant low frequency noise sou rces of InAlAs/InGaAs MODFET transistors in the ON state are generated by deep traps distributed within the ''bulk'' InAlAs barrier and buff er layers, For reverse gate bias, the gate current appears to be the d ominant contribution to the channel LFN, whereas both the gate current and the drain and source ohmic contacts are the dominant sources of n oise when the device is biased strongly in the ON state. Heterojunctio n FET's on InP substrate with InP barrier and buffer layers show signi ficantly lower LFN and appear to be more suitable for applications suc h as nonlinear circuits that have noise upconversion.