Research On New Structure Of AlGaN/GaN HEMT Power Device

Gallium nitride(GaN) has attractive advantages for power electronics for its large critical field, wide energy band gap, and high electron saturation velocity, compared with Si as the first-generation of semiconductor material and GaAs as the second-generation semiconductor material.Two-dimensionalelectron gas(2DEG),formed by large polarization effect at AlGaN/GaN hetero structure has high density and large mobility which make the Gallium nitride a potential material for powerelectronics application. However, the present study has show the AlGaN/GaN HEMT devices do not have high breakdown voltage as expected for the unintentionally doped GaN buffer layer showsn-type conductivity, with carrier density of 1014~1015 cm-3,and the electric field may concentrate near gate.This paper focuses on the technologies enhancing AlGaN/GaN HEMTbreakdown voltage aftera readingand analyzing a lot of literature and mastering the theory analysis with simulationverification.One of the technologies is using field plate.Field plate is a proven technology,and its process is simple and easy to implement.Simulation shows that after the introduction of a floating field plate, AlGaN/GaN HEMT has a smoothelectric field in the channel enhancing device’s breakdown voltage, beside the floating field plate has little effect on the high-frequency characteristics of the device. It can further improve breakdown voltage if the field plate is shorter. Compared with the one without field plate, the breakdown voltage increases from 50 V to 240 V.Another device is the vertical AlGaN/GaN HEMT with p-doping buried layer. The device does not have current collapse effect and buffer current leakage. However, the normal vertical AlGaN/GaN HEMT also shows low breakdown voltage. After understanding how the vertical AlGaN/GaNHEMT works,we propose a new vertical device with p-doping buried layer. The result show the wide,length,position and doping concentration of p-doping buried layer are important with sentaurus to simulate the new device. The more the doping concentration is, the more the breakdown voltage improve, for example with p-doping buried layers,the device’s breakdown voltage improve from 1680 Vto 3050 V.A brief summary of the full text has been made.