Model Research For HEMT Based On Sunface Potential

Currently, the microwave / millimeter-wave devices and its circuit have become increasingly prominent in industrial applications, which have become the hot spot of microelectronics technology research. With the development of microelectronics technology, the requirements of the devices become more sophisticated and the limitations of silicon-based devices and its circuit are also noticeable. Compared to the MOS silicon devices of industry's mainstream, compound HEMT devices hold clear advantages in the field of ultra-high-speed, low power, low noise and high voltage, etc., especially in the high-frequency and high power circuit applications.As HEMT materials and devices become more complicated, importance of researching HEMT models become more apparent. A sophisticated HEMT model is very meaningful for improving efficient of circuit design, reducing the circuit research and development cycle, saving circuit development costs and helping to make products more industrialization. Compared with development of empirical models, that of physics-based models for HEMT is very slow. As PSP model is becoming the industry standard model for MOSFET in deep sub-micron size, the advantages of surface potential model is gradually recognized by people. Previous studies on the HEMT demonstrate that, bringing in the concept of surface potential in HEMT modeling is feasible. But the research of surface potential based HEMT modeling is rare in the past work.Referring to the surface potential based analysis method for MOSFET model, this paper use the concept of surface potential to establish a physical based HEMT theory model. First, physical structure of the device is analyzed, and surface potential equation is established using the relationship of the energy band and Poisson's equation of HEMT channel, then surface potential is calculated by using analytical approximate method. Finally, current and charge equations are established through surface potential. The results show that, this model can characterize HEMT device current and charge characteristics in a basic extent, which demonstrate the model has a positive meaning for the HEMT physics model theoretical analysis and future industrial applications. There is rare research work on the surface potential in HEMT modeling, from this point of view, the reseach of this paper has a ground-breaking significance for widening HEMT modeling. However, due to the discontinuous and approximation of model equations, there are several errors in connection point and threshold point of channel, which is the problem to overcome in the future work.This thesis is arranged as follow: HEMT and background of its model as well as relative previous work are described in Chapter I. the basic structure of the HEMT devices, the physical operation mechanism as well as traditional physical analysis are discussed in Chapter II, briefly. In Chapter III, the method of establishing original surface potential model, such as Pao-sah model and the charge-sheet model for MOSFET is introduced, and surface potential analytical solutions and current/charge equations of the PSP model are briefly discussed. In Chapter IV, analysis and establishment of HEMT surface potential model is emphasized. And finally, simulation results are analyzed in Chapter V.