Errors Limiting Split-CV Mobility Extraction Accuracy in Buried-Channel InGaAs MOSFETs

The accuracy of the split-CV mobility extraction method is analyzed in buried-channel InGaAs MOSFETs with Al2O3 gate dielectric and InP barrier, through a “simulated experiment” procedure using two-dimensional numerical device simulations preliminarily calibrated against experimental IV and CV curves. The different error sources limiting the method accuracy are pointed out. It is suggested that, as a result of these errors, the split-CV method can appreciably underestimate the actual channel mobility in these devices, with an error >20% and >50% on peak and high-VGS mobility, respectively. The method should therefore not be adopted for accurate mobility measurement in this operating regime, but only as a fast response technique providing a conservative estimation of channel mobility. Moreover, the method provides mobility values that rapidly drop below the peak value for decreasing VGS. It is shown that this behavior can be an artifact of the extraction method, that may mask physical mechanisms causing real mobility drop with decreasing channel carrier density like Coulomb scattering mechanisms. This poses limitations to the adoption of split-CV mobility as a reference for mobility model assessment in this operating regime. The proposed methodology can be applied to other III-V field-effect transistors, including both heterostructure-based and inversion-mode devices.