Design And Manufacture Of Lateral Structure AlGaN/GaN Schottky Barrier Diode

In recent years,gallium nitride（GaN）has become a hot topic of research at both the national and international level due to its excellent characteristics such as wide bandgap,high voltage resistance and the ability to generate two-dimensional electron gas without doping.The GaN-based AlGaN/GaN heterojunction Schottky Barrier Diode（SBD）is widely used in power,electronics and communication applications due to its high voltage stability,low on-resistance and high switching frequency.In this thesis,based on the physical properties of AlGaN/GaN heterojunction and the operating principle of SBD devices,the following improvements have been made in the fabrication process and device structure of AlGaN/GaN SBD devices:Firstly,the main AlGaN/GaN-SBD device flow process was optimised,and the influence of different Ti/Al metal ratios and thicknesses on contact resistance was studied for the ohmic electrode,with the lowest contact resistance of 8.51×10^-6Ω·cm²at Ti/Al=20/120 nm.The annealing time and temperature of Schottky electrodes were improved to study the effect of different annealing times and temperatures on AlGaN/GaN-SBD device performance.Device forward characteristics were optimised at 4 min anneal time and 500°C anneal temperature.Next,the effect of the width,spacing and number of floating mental rings on the inverse characteristics of the device was simulated using Silvaco software.The maximum electric field contribution to the device was achieved at 2μm ring width and3μm spacing,and the breakdown voltage increased from 501 V to 858 V when the number of rings increased to three.The test results showed that the floating metal ring structure can effectively increase the breakdown voltage of the device from 398 V to692 V compared to the device without the floating metal ring structure,while the forward current of the device decreased as the number of floating metal rings increased.Finally,the effect of the finger structure on the electrical characteristics of the device was simulated using Silvaco software.Different finger spacing,number of fingers and field plate structure were used to optimise the device.The results showed that the electrical characteristics of the device were best at a finger spacing of 20μm,the forward current of the device increased continuously as the number of fingers increased,and the breakdown voltage of the device was increased from 762 V to 1489V by constructing the field plate structure.The devices were then prepared and tested according to the simulation results.The test results showed that the forward current density of the device increased from 547 A/cm² to 1020 A/cm² and the forward current from 0.12 A to 2.09 A after the number of insertion fingers was increased from 1 to 30at a forward voltage of 3 V.The breakdown voltage of the device increased from 418 V to 833 V by the construction of the 3μm field plate structure.