Ultraquasi-hydrodynamic electron transport in submicrometer field effect MIS transistors and heterotransistors

Abstract

It is shown that electrons in the channel of submicrometer field effect transistors have no time to be heated to quasi-steady-state temperatures corresponding to a balance between the Joule heating and thermal relaxation. This “underheating” contributes to an increase in the effective mobility of charge carriers as compared to the value of μ(E) corresponding to the drift-diffusion approximation. Using a reduction of the thermal-balance equation by eliminating the relaxation-related term, a simple analytical expression is obtained for current-voltage characteristics. In particular, the saturation current in the developed ultraquasi-hydrodynamic model is found to be proportional to (VG-Vt)3/2. The results of measurements of characteristics of the test GaAlAs/InGaAs/GaAs P-HEMTs with the channel length of about 0.3 µm are reported; these results verify the adequacy of the developed model, the accuracy of which can only increase with a further decrease in the channel length.