The Research On AlGaN/GaN Heterostructure Devices To Enhance The Concentration Of 2DEG

Due to the excellent properties of Chemical stability, high temperature resistance and corrosion resistance, GaN Semiconductor Materials is suitable to the manufacturing of the device of optoelectronic (blue, green and ultraviolet light, etc), anti-radiation, high-frequency and high-power. All of the excellent properties of GaN make up the inherent drawbacks of the previous two generation semiconductor materials well, which has become one of the widespread concern focuses in the field of microelectronics at present.AlGaN/GaN heterostructure field effect transistor (HFET) is a kind of GaN device based on the AlGaN/GaN heterojunction materials. Besides of several inherent advantages of GaN material, the polarization effect of AlGaN/GaN HFET device that produced from the different of lattice constance at the interface of heterojunction makes it could yield high concentrations two-dimensional electron gas (2DEG) even in the case of AlGaN barrier layer undoped. It is noteworthy that the concentration of 2DEG is sensitive to several factors such as Al fraction, the thickness of barrier layer, degree of the strain relaxation and gate bias voltage, and its value directly affects the Electrical Properties of AlGaN/GaN HFET. This paper investigates these factors that affect the 2DEG concentration, which has great significance to research and extension of such devices.Firstly, this paper surveyed the domestic and overseas developing situation of the AlGaN/GaN devices, proposed the research significance and value of the subject, and briefly introduced the software environment of process and device physics characteristic simulation. Secondly, the author discussed the basic material characteristic of GaN (including crystal structure and photoelectric characteristics) and the working principle of AlGaN/GaN heterojunction. Focused on the physical models, (mainly the polarization effect model, the mobility model and carriers SRH, etc), which are used by the device simulation of AlGaN/GaN heterojunction, the author selected these models and modified their parameters. Designed the structure of AlGaN/GaN device, and optimized the main consideration for each factor (Including Al fraction and the thickness of AlGaN barrier layer, degree of strain relaxation gate bias voltage, etc) of the scheme of simulation experiment and surface response model (RSM turbulence) optimization analysis (mainly based on the DoE method and theory, and build a reasonable RSM turbulence, study of various factors, the influence of device characteristics by optimizing the design satisfied the requirement of design manufacturability area). At last, this paper discussed and analyzed the results of the simulation experiment, especially the factors which influences the concentrations and export characteristics of the 2DEG.In connection with the requestments of the device's design, this paper chose the factors affect the 2DEG concentrations used leakage current Id and transconductance gm as optimization goals to build RSM model, and got the optimization screen which included all kinds of influences'factors.Because of the imperfection for the AlGaN/GaN HFET devices'models in library of Simulation environment, the author should select many different models and modify their important parameters. This process that is directly related to whether device simulation has significance is the key stage of the whole paper work.The research displays that the concentrations of 2DEG could apparently rise with A1 fraction when the barrier layer thickness of AIGaN is approaching 30nm. Meanwhile, with the parameter of Al fraction and the thickness of barrier layer is increasing, it will make rise the degree of strain relaxation of the AlGaN barrier layer, which will decrease the conduction characteristics of the current. When Al fraction is fixed, the concentrations of 2DEG is lower, the pinch-off voltage will increase with the increase of the degree of strain relaxation. When the degree of strain relaxation is fixed, the concentrations of 2DEG will increase and the pinch-off voltage will decrease with the increase of A1 fraction.As far as now, it is relatively uncommon work of computer simulation studies and analysis for AlGaN/GN HFET devices by virtue of Design for Manufacting (DFM) tools in China. Therefore, this research makes a certain basis of the DFM for the further study of AlGaN/GaN devices and correlative Integrated Circuits (IC); it is at the forefront in the domestic homogeneous studies; the results of the study have the centain reference and application value in theory.