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 a Al₂O₃ gate dielectric and an InP barrier, through a “simulated experiment” procedure using 2-D numerical device simulations that are preliminarily calibrated against experimental I-V 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 of >;20% and >;50% on peak mobility and high-V_GS 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 V_GS. 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-CV mobility 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.