| Among the key high power devices, the research of the solid state source microwave devices has found its wide applications. The impact ionization avalanche transit time diode(IMPATT),as one of the most powerful solid state source of microwave devices,has gained more attention with the development of science and technology. Meanwhile,with the improvement of semiconductor process technology,manufacturing of Ga N which is the representative of the third generation of wide band gap semiconductor material has become a reality. The choice of semiconductor materials has been focused on wide-band gap materials. The reason why Ga N material is selected in the paper is in view of its wide band gap, high saturation drift velocity and high breakdown electric field.IMPATT as a negative resistance device is capable of producing a stable sine wave. This paper is based on the negative resistance characteristics of the device and the further study is conducted in the platform of Silvaco-Atlas. The main findings are as follows:1. A further research on terahertz field and a familiarity of the current condition of IMPATT is conducted. A discussion of the working mechanism of IMPATT is made including the analysis of the breakdown characteristics, static characteristics and the effect of the temperature and space charge and other related factors.2. A few different device simulation models of drift-diffusion model, the energy balance model, hydrodynamic model are discussed in details with emphasis on the analysis of energy balance model.3. The Atlas of Silvaco platform is described in details. Two different kinds of doping of single-drift region IMPATT are conducted with physical modeling in the Atlas and an analysis of device structure is made. The length of the drift region and avalanche region and the best working frequency are calculated. At the same time, the simulation of breakdown voltage is made. The breakdown voltage of the diode is extracted by obtaining the I-V characteristic curve of IMPATT diode. The difference of voltage and current in phase delay exists from observing the picture of conductance current with the presence of the bias voltage, which verifies the negative resistance characteristics of IMPATT diodes.4. The circuit-level model of the device is made in the Mixed-mode of Atlas. Firstly, the resonance condition of diode and the parameter values for each device in the resonant circuit are obtained. The resonant circuit of the single drift region of Ga N IMPATT is built and then a stable sine wave output is got using the drift-diffusion model. The diode with energy balance model is emphasized on in the simulation. The discussion of different mobility models and impact models are discussed. The comparison of output power and so on in the drift diffusion model and energy balance model is down and from which we can obtain that energy balance model is more accurate than drift-diffusion model when analysing the AC characteristics of sub-micro IMPATT diode.In summary, the comparison of the drift-diffusion model and energy balance model is made through the simulation of Ga N IMPATT diode which deepened our understanding of the terahertz IMPATT diode. The excellent characteristics of Ga N IMPATT diodes will make it become the most important terahertz microwave solid source in the future in the field of terahertz. |
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