Noise parameter modeling for InP-based pseudomorphic HEMTs [InAlAs-InGaAs]

The effect of electron mobility (/spl mu//sub n/) on noise properties for InP-based pseudomorphic HEMTs has been analyzed based on the impedance field model. The analysis predicts that increasing /spl mu//sub n/ improves the minimum noise figure (F/sub min/) and associated gain not only because the unity current gain cut-off frequency increases but also because the source resistance is reduced. The analysis also predicts that increasing /spl mu//sub n/ reduces the input noise resistance due to higher transconductance but hardly influences the noise-optimum impedance. Furthermore, it is predicted that the decrease in F/sub min/ with increasing /spl mu//sub n/ becomes less significant above 11000 cm/sup 2//Vs due to larger diffusion noise. Calculated results compare well with the measured scattering and noise parameters for In/sub x/Ga/sub 1-x/As(x=0.53, 0.7, and 0.8) channel devices. Similar dependence of noise parameters on /spl mu//sub n/ is shown in the theoretical and experimental results.