The Investigation For Vertical Gallium Nitride Schottky Barrier Diodes

With the development of technology,new technology products,such as switch,smart phone,electric car,renewable energy power generation and so on,give new re-quirements for power device.As the energy problems worsens,we hope to save re-sources as much as possible.This requires that performance of power device should be increasing,and traditional Si-based power device can't meet the demand.The third generation semiconductor Gallium Nitride(GaN)and Silicon Carbide(SiC)that are known as high performance come into our sight.Compared to Si and SiC,GaN has the wide band gap(3.43 eV),the high electron mobility(1245 cm2/V·s)and the high electron saturation velocity(2.5 × 107 cm/s).It can achieve higher breakdown voltage and lower on-resistance,which is more suitable for fabricating power devices.Accord-ing to the device structure,compared to the lateral structure,vertical diodes can achieve smaller device size and eliminate current blocking effects,which is more beneficial to achieving high breakdown voltage,low on-resistance and high integration.In addition,compared to heteroepitaxy,homoepitaxial GaN has lower dislocation density and inter-facial stress,which can achieve greater crystal quality.With the development of GaN growth,there have been GaN substrates with low dislocation density(106 cm-2)in the market,which provides great material basis for the deveploment of vertical GaN-on-GaN Schottky Barrier diodes(SBD).Currently,SBD is moving to the direction of high breakdown voltage,high Ion/Ioff ratio and low on-resistance.Devices with high break-down voltage can work stably in high voltage.Device with high Ion/Ioff ratio and low on-resistance can achieve better switch and lower loss.In this paper,we designed and simulated vertical GaN SBD by using TCAD(Tech-nology Computer Aided Design).Then micro-nano proccessing technolohy was used to fabricate vertical GaN SBD,such as UV lithography,inductively coupled plasma etching and ions implantation,and obtained the following results:1.The GaN epilayers growth by metalorganic chemical vapor deposition(MOCVD)were characterized by atomic force microscopy(AFM),cathodoluminescence(CL),high-resolution X-ray diffraction(HRXRD)and secondary ion mass spectroscopy(SIMS),which can get surface morphology,dislocation density and background concentration.The results show a smooth surface and high crystal quality of GaN epilayer with low background concentration,which meets the requirements of fabricating the vertical GaN SBDs2.The vertical GaN SBD was designed and simulated by TCAD,which is in order to analysis the distribution of electric field in different structures at reverse bias.What's more,the parameters of ions implantation were simulated by the stopping and range of ions in matter(SRIM),such as implanted energy and doses.According to the simulated results,we designed and fabricared vertical GaN SBDs.3.Micro-nano proccessing technolohy was used to fabricate vertical GaN SBD,such as UV lithography,inductively coupled plasma etching(ICP)and Boron ions im-plantation.We compared SBD with and without Boron ion implanted termination(BIT).We found that,compared with the GaN SBD without BIT,the SBD with BIT enhanced breakdown voltage up to 585 V,had 105 × reverse leakage reduction and obtained a high Ion/Ioff ratio of 108.What's more,the Schottky barrier height of SBD was in-creased from 0.68 eV to 0.82 eV by using Boron ions implantation.It means that Boron ions implantation technology can effectively increase breakdown voltage and suppress reverse leakage current.