Process And Structure Optimization And Electrical Characterization Of AlGaN/GaN Heterojunction Schottky Barrier Diode

GaN material is often used to build wide band semiconductor devices due to their wide band gap,high temperature resistance,radiation resistance and high hardness.Among them,AlGaN/GaN heterojunction Schottky barrier diode（SBD）is widely used in power electronics and RF communications due to their high electron mobility,high thermal stability,low high frequency loss and strong high frequency stability.In this thesis,the preparation process of AlGaN/GaN heterojunction Schottky barrier diode is optimized;the notch etching depth and area of notch-anodized AlGaN/GaN heterojunction Schottky barrier diode is tuned;the p⁺protection ring（PGR）AlGaN/GaN SBD and AlGaN/GaN heterojunction multi-channel SBD is simulated and structurally optimized using Silvaco TCAD software.The details of the study are as follows:Firstly,the ohmic electrodes was optimized by adjusting the Ti/Pd ratio,and the effect of annealing parameters and Si O₂passivation layer on the electrical characteristics of the devices was studied.The experimental results showed that the specific contact resistance of the ohmic electrode is the smallest at 1.04×10^-5Ω·cm²at a Ti/Pd ratio of 1:5;the best electrical performance is achieved when the annealing temperature of the ohmic electrode is 700℃and the annealing time is 3 min;the inclusion of Si O₂passivation layer in the device effectively reduces leakage current.and increases the forward current.Next,the effect of depth and area of recess which etched on the forward and reverse electrical characteristics of the devices was studied.The experimental results showed that the forward current and reverse breakdown voltage decrease with increasing the depth of recess of the devices,the reverse breakdown voltage decreases from 513 V to 432 V;the forward current and reverse breakdown voltage increase with increasing the area of recess of the devices,the reverse breakdown voltage increases from 439 V to 587 V.Then,the effect of the width and number of p⁺type protection ring（PGR）on the forward and reverse electrical characteristics of the devices was analysed using Silvaco-ATLAS software.The simulation results showed that when the width of the PGR of the devices increases,the forward current decreases and the reverse breakdown voltage increases,the reverse breakdown voltage increases from 576 V to665 V;when the number of the PGR of the devices increases,the forward current and reverse breakdown voltage both increase,the reverse breakdown voltage increases from 581 V to 817 V.Finally,the static characteristics of AlGaN/GaN heterojunction multichannel SBD are analysed in depth using Silvaco-ATLAS software.The simulation results show that:the multi-channel SBD reduces the series resistance and reverse breakdown voltage and increases the cut-off frequency;the device performance is best when the Al component in the first channel is 0.2 or 0.25,and the Al components in the second,third and fourth channels are 0.3 or 0.4;the forward current increases as the thickness of the barrier layer increases;the forward current decreases slightly with increasing trench layer thickness.In summary,the preparation process and structure of AlGaN/GaN SBD devices are optimised and the effects of various structural parameters on the electrical characteristics of the devices are analysed through experiments and simulations.This study provides guidance on the performance optimization of AlGaN/GaN SBD.