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

The accuracy of the split-CVmobility extraction method is analyzed in buried-channel InGaAs MOSFETs with a Al2O3gate dielectric and an InP barrier, through a “simulated experiment” procedure using 2-D numerical device simulations that are preliminarily calibrated against experimentalI-VandCVcurves. The different error sources limiting the method accuracy are pointed out. It is suggested that, as a result of these errors, the split-CVmethod can appreciably underestimate the actual channel mobility in these devices, with an error of >;20% and >;50% on peak mobility and high-VGSmobility, 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 decreasingVGS. It is shown that this behavior can be an artifact of the extraction method, which may mask physical mechanisms causing a real mobility drop with decreasing channel carrier density, such as Coulomb scattering mechanisms. This poses limitations to the adoption of split-CVmobility as a reference for mobility model assessment in this operating regime. The proposed methodology can be applied to other III-V FETs, including both heterostructure-based and inversion-mode devices.