低反向漏电自支撑衬底AlGaN/GaN肖特基二极管  

Investigation of AlGaN/GaN Schottky barrier diodes on free-standing GaN substrate with low leakage current

作　　者：武鹏[1] 张涛[1] 张进成[1] 郝跃[1] Wu Peng;Zhang Tao;Zhang Jin-Cheng;Hao Yue(National Key Discipline Laboratory of Wide Bandgap Semiconductor,Xidian University,Xi’an 710071,China)

机构地区：[1]西安电子科技大学,宽带隙半导体技术国家重点学科实验室,西安710071

出　　处：《物理学报》2022年第15期299-305,共7页Acta Physica Sinica

基　　金：国家自然科学基金(批准号:62104185);国家杰出青年科学基金(批准号:61925404);中央高校基本科研业务费(批准号:JB211103)资助的课题。

摘　　要：氮化镓材料具有大的禁带宽度(3.4 eV)、高的击穿场强(3.3 MV/cm),在高温、高压等方面有良好的应用前景.尤其是对于铝镓氮/氮化镓异质结构材料而言,由极化效应产生的高面密度和高迁移率二维电子气在降低器件导通电阻、提高器件工作效率方面具有极大的优势.由于缺乏高质量、大尺寸的氮化镓单晶衬底,常规氮化镓材料均是在蓝宝石、硅和碳化硅等异质衬底上外延而成.较大的晶格失配和热失配导致异质外延过程中产生密度高达10^(7)—10^(10) cm^(–2)的穿透位错,使器件性能难以进一步提升.本文采用基于自支撑氮化镓衬底的铝镓氮/氮化镓异质结构材料制备凹槽阳极结构肖特基势垒二极管,通过对欧姆接触区域铝镓氮势垒层刻蚀深度的精确控制,依托单步自对准凹槽欧姆接触技术解决了低位错密度自支撑氮化镓材料的低阻欧姆接触技术难题,实现了接触电阻仅为0.37Ω·mm的低阻欧姆接触;通过采用慢速低损伤刻蚀技术制备阳极凹槽区域,使器件阳极金属与氮化镓导电沟道直接接触,实现了高达3×107开关比的高性能器件,且器件开启电压仅为0.67 V,425 K高温下,器件反向漏电仅为1.6×10^(–7) A/mm.实验结果表明,基于自支撑氮化镓衬底的凹槽阳极结构铝镓氮/氮化镓肖特基势垒二极管可以有效抑制器件反向漏电,极大地提升器件电学性能.Benefiting from the excellent properties of GaN with a wide bandgap of 3.4 eV as well as high critical field of 3.3 MV/cm,GaN-based devices prove to be a promising candidate in extreme conditions.Especially,highdensity high-mobility two-dimensional electron gas(2DEG) induced by spontaneous piezoelectric polarization in AlGaN/GaN heterostructure enables AlGaN/GaN device to lower on-resistance(RON).However,owing to the lack of free-standing GaN substrate with large size and high quality,the epitaxis of GaN is always based on hetero-substrate such as Al_(2)O_(3),Si and SiC,which shows large lattice mismatch and thermal mismatch.The large mismatch between GaN and substrate leads to high dislocation as well as high leakage current(IR) of GaN devices.In this work,high-performance AlGaN/GaN Schottky barrier diode with low IR and low turn-on voltage(VON) is fabricated on a 3-inch free-standing GaN substrate with C-doping GaN buffer layer to suppress IR.Owing to the suppressed dislocation density of the AlGaN/GaN epitaxial wafer on free-standing substrate,low Ohmic contact resistance(RC) is difficult to achieve the suppressed penetration of Ohmic metal into 2DEG channel,which is adverse to the high current density.In this work,a low RC of 0.37 Ω·mm is obtained by onestep self-aligned Ohmic process,including the etching of partial AlGaN barrier layer and lift-off of Ohmic metal.The 2DEG is formed under the effect of residual AlGaN barrier layer,and the short distance between 2DEG and Ohmic metal contributes to lowering the value of RC.The groove anode region is defined by the low damaged inductively coupled plasma process with a low etching rate of 1 nm/min,and the total depth is 35 nm,confirmed by atomic force microscope.Fully removing the AlGaN barrier layer from the anode region makes the anode metal directly contact the 2DEG channel,thereby improving the performance of the fabricated AlGaN/GaN Schottky barrier diode(SBD) with a low VON of 0.67 V,low IR of 3.6 × 10^(–8) A/mm,and an ION/IOFF ratio of up to 3 × 10~7

关 键 词：自支撑氮化镓衬底 肖特基势垒二极管 低反向漏电 铝镓氮/氮化镓 

分 类 号：TN311.7[电子电信—物理电子学]