QUASI-TWO-DIMENSIONAL DRIFT-DIFFUSION MODEL OF HEMT TRANSISTORS
The development of HEMT transistors structure along with its design and modelling methods is a matter of high interest. That may be associated with its widespread application in RF systems. We have developed a new quasi-two-dimensional model based on the drift-diffusion approximation, which provides an adequate current-voltage and V-C characteristics of AlGaAs/GaAs HEMT transistor. The intervalley transitions along with the field-dependent mobility and the presence of a whole charge in the channel were taken into consideration. That provided a possibility of accurate calculation the non-uniformity of the spatial distributions of potential, electrical field, electron temperature, mobility and electron drift velocity. It also provides an "accuracy-complexity" relationship that satisfies both research and design objectives. The proposed model demonstrates high ability to evaluate the time delay of HEMT transistor since it is capable of quantitatively estimating the intrinsic capacitances values as well as the transit time of electrons beneath the gate. The validation of the model was checked by comparison the calculated current-voltage characteristics with experimental data for AlGaAs/GaAs HEMT transistor with a channel length of 500 nm. The physical nature of the proposed model makes it possible to use it as a tool for analyzing and enhancing the parameters of HEMT transistors. For the same reason it can be utilized for simulation other field-effect devices.