S-Parameter and Equivaleat-Circuit-Parameter Statistics

We compare the ability of three different equivalent-circuit extraction methods to give ensembles of model parameters that accurately predict not only average S-parameters but the S-parameter statistics the standard deviations and intercorrelations between the real and imaginary parts. Measurements were made for 400 GaAs MESFET's fabricated on a single wafer with an MBE-grown active layer. Data is compared for different biases. We find that bimodal distributions give unphysical correlations that the equivalent-circuit models fail to model. The possibility of using uncorrelated equivalent-circuit values is also discussed.