α相Ga2O3基半导体异质结构外延设计及高耐压HEMT器件应用

The demands for the rapid development of power electronics towards the wide applications in the fields of energy, information and defense technologies is driving academic and industrial research efforts in the search for novel desirable power electronic materials. Owing to unique advantages of larger bandgap, higher breakdown voltage, lower on-resistance as compared to beta-phase Ga2O3, GaN and SiC materials, an emerging material named alpha-phase gallium oxide (α-Ga2O3) is found desirable for developing power electronic devices with performance of high breakdown voltage and low loss. This project aims at developing non-equilibrium epitaxial technology to synthesize high quality single crystalline alpha-phase aluminum gallium oxide and related heterostructures, realizing high mobility two dimensional electron gas at hetero-interface through the modulation doping technique, and finally demonstrating alpha-Ga2O3 based high electron mobility transistors. To achieve these objectives, this project will focus on solving series of scientific and technical issues including structural phase controlling, strain engineering, bandgap tuning and modulation doping as well as the investigation of fundamental properties. The main strategies of this project include: (1) To realize state-of-the-art epitaxy of α-Ga2O3 and its related heterostructures by combining metal organic chemical vapor deposition (MOCVD) and laser-molecular beam epitaxy (LMBE) techniques. The growth modes, dislocation formation mechanisms and defect behaviors will be conducted. The digital superlattice and graded compositional buffers are proposed to suppress the phase segregation and reduce the dislocation densities in the epilayers. (2) To implement delta-doping technique and attempt back-barrier structure design to enhance the interfacial transport capability and breakdown voltage. The band structure, carrier transport and scattering mechanisms will be investigated. (3) To demonstrateα-Ga2O3 based HEMT prototype devices by developing key fabrication processes such as metal contact and passivation. The correlation between device performance and material properties will be established to feedback the optimization of material epitaxy and device fabrication. The success of this project is expected to provide device demanded materials and strategic technologies, and make fundamental and innovative contributions in the field of power electronics.

面向能源、信息、国防等领域的功率电子产业的快速发展亟需探索和发展新型功率半导体材料以满足其迫切需求。α相Ga2O3因其优异的物理特性，是发展新型高性能功率电子器件的理想材料，具有广阔应用前景。本项目提出发展非平衡生长技术外延低位错密度、高电子迁移率、高电子限域的α-Ga2O3基异质结构，并研制HEMT原型功率器件。项目将重点解决物相调控、应变工程、能带剪裁、缺陷控制和界面设计等关键科学问题，包括：揭示非平衡生长机理和生长模式，通过合金数字超晶格等应力调控手段抑制相分凝和降低缺陷密度；采用δ掺杂、插入层和背势垒结构等设计，协同调控界面二维电子气的分布和输运性能；研究能带结构、电-声子互作用、缺陷行为、载流子散射机制；发展金属接触和钝化等关键工艺控制界面态密度，建立材料缺陷与器件性能的内在联系。本项目以期对新型HEMT功率器件的发展提供关键材料技术与物理支撑，在电子电力器件领域做出基础性创新。

本项目以发展新型α-Ga2O3基功率器件为目标，围绕物相调控、应变工程、能带剪裁、缺陷控制和界面设计等关键材料科学问题开展研究，针对大失配外延的重大难题，发展Mist-CVD和HVPE等外延方法，研发出核心生长设备，基于应变工程突破了位错抑制和载流子调控等关键技术，在蓝宝石上实现了高品质、低位错密度α-Ga2O3异质结构外延和原位n型可控掺杂，率先揭示了晶格失配引起的应变对α-Ga2O3外延层中位错滑移、融合和湮灭的动力学规律。2英寸蓝宝石基的α-Ga2O3螺位错密度<2×106 cm-2、厚度均匀性>97%，具有原子级表面平整度，质量指标达到同期报道领先水平，已为国内外多家著名研究机构提供高品质Ga2O3复合晶圆，并获高性能器件验证；探索和外延与α-Ga2O3晶格匹配的具有刚玉结构的p型α-Ir2O3单晶薄膜，并制备出高Ga组分的 (IrxGa1-x)2O3(x=0.05-1)合金，实现了与α-Ga2O3晶格和带隙双重匹配的p型氧化物，并研制出具有良好整流特性的α-Ga2O3/α-Ir2O3 p-n异质结二极管，为Ga2O3双极性器件设计提供了新的自由度。理论结合实验研究了不同类型位错对载流子浓度的补偿作用及其散射对载流子迁移率崩塌的影响机理；深入揭示了α-Ga2O3基异质结界面及漂移层中缺陷的空间分布、能级位置及其对载流子的俘获行为，阐明了II型异质界面能带弯曲和载流子隧穿复合的共性机制，并提出了光生空穴积累导致界面势垒降低的物理模型，澄清了Ga2O3日盲探测器外量子效率普遍偏高的内在机理。针对响应慢、提前击穿等器件问题，开创了氧化镓基双极型异质外延集成技术，SBD等功率器件性能达国际领先水平，NiO/Ga2O3异质外延集成技术已被西电和中电13所等单位采用，共同研制出Ga2O3 基HJFET，功率因子为0.39 GW/cm2,为目前Ga2O3基功率开关器件最高水平；研制出Au/α-Ga2O3/ZnO同型异质结肖特基雪崩二极管(APD)，其雪崩增益(>5000)和响应度均为目前Ga2O3基异质结日盲探测器报道最高值，在自主外延的高品质α-Ga2O3外延层上引入Rh和Al金属微纳结构设计，研制出超低暗电流(<0.1pA)和高探测率的等离激元增强日盲探测器，突破了响应度和响应速度相互制约的瓶颈。