Study On Characteristics Of GaN Gunn Diode Using Energy Balance Model

Terahertz (THz) technology is a new cross-disciplinary research area which has made rapid development recently, involves physics, materials science, biology, medical science and so on. The terahertz regime covers wideband electromagnetic radiation area from 0.1 THz to 10THz frequency range, sandwiched between the microwave and infrared, bridges the gap between electronics and optics, contains a wealth of physical connotation, and thus has a wide variety of applications. Among all the solid state sources already available, Gunn diodes, based on the negative differential resistance (NDR), provide a solution for a low-cost, low noise and high power microwave radiation sources, so that have a great potential in the terahertz application. As Wide-bandgap semiconductor material GaN offers a lot of advantages such as high bandgap, high saturation velocity, and high breakdown electric field, it is commonly used in Gunn devices. As a result, the study of GaN Gunn diodes have became particularly important. However, the mature Gunn diodes haven’t been fabricated, so the study of Gunn diodes can only be based on software with theoretical analysis.Previous study of Gunn diodes is often based on the drift-diffusion (DD) model, however the drift-diffusion model ignores nonlocal effect, such as the velocity overshoot, inevitably affect to the accuracy of the simulation. Compared to DD model, Energy Balance (EB) model includes non-localized carrier transport phenomena, and thus is more accurate for spatiotemporal domain and chaos in the channel of GaN Gunn diodes. The EB model is embedded into Silvaco-ATLAS platform, which is an effective approach for device-fabrication-oriented simulation. By using ATLAS platform, we propose a uniformly doped n+-n-n+ structure in transit regions of GaN Gunn diodes, and then analyze the device features related to structure parameters based on EB model. Results show that GaN Gunn diodes can work within the scope of the terahertz spectrum and have higher output power compared to the GaAs Gunn diodes. Therefore GaN Gunn device will have a great application prospect in the field of terahertz technology.On the other hand, in the view of there is little research work reported on the thermal prosperities of Gunn diodes. By the use of ATLAS-GIGA platform, we present a numerical analysis on the electric and thermal behaviors of notch doped n+-n--n-n+ structure GaN Gunn diodes based on Non-isothermal Energy Balance (NEB) models which is a transport model (EB model) coupled with a thermal model. It is shown that the real temperature in the device involves strong modifications in the electrical behavior of Gunn devices:output power density as well as oscillation frequency decreases when the lattice temperature is taken into account. As the NEB model takes into account the local temperature at each point and the influence on transport properties, it accurately describes the behavior of the physical quantities of GaN based Gunn diodes, thus making it possible to optimize the device.In conclusion, we develop a numerical analysis on the electric and thermal behaviors of GaN Gunn diodes, in order to take into account the nonlocal effect and the self-heating effect at the same time, thus making a better reflect the real working environment, and then providing a useful way to optimize the Gunn diodes design.