Van der Waals Ga2O3 functional materials epitaxy: Revolutionary power electronics

范德华 Ga2O3 功能材料外延：革命性的电力电子学

• 批准号: EP/X015882/1
• 负责人: Martin Kuball
• 金额: $ 25.67万
• 依托单位: University of Bristol
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2023
• 资助国家: 英国
• 起止时间: 2023 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=EP%2FX015882%2F1
• 关键词: Van; der; Waals; Ga2O3; functional

The imminent climate risks for our planet have been highlighted by the UN's Intergovernmental Panel on Climate Change (IPCC) calling it "code red for humanity" in its scientific report in August 2021. Presently, nearly all energy conversion power electronics use Silicon (Si), which is relatively inefficient, wasting energy as heat. In fact, 72% of global primary energy consumption is wasted, of which 20% could be saved with new power electronics! Wide bandgap devices using GaN and SiC are entering the market, but they either do not sustain high enough voltages or are too expensive for widespread use, e.g., in smart grids. Ultrawide bandgap Gallium Oxide (Ga2O3), with efficiency far exceeding that of narrow bandgap Si, has emerged as a transformative contender with low cost and >1-2 kV, even 10 kV voltage capability, with potential for a massive >100x reduction in power conversion efficiency losses. Considering Ga2O3's high Baliga figure of merit, the metric determining how beneficial a material is for power devices, it has potential to even exceed current wide bandgap power devices (GaN, SiC), now replacing incumbent Si power electronics, by more than a factor of 5-10 in performance.In this project, we target high voltage power devices using van der Waals epitaxy of functional Ga2O3 as a transformative and revolutionary vehicle to open a new research field for low cost high voltage power devices. This form of epitaxy uses an intermediate layer, which reduces the substrate-epitaxial layer interaction, enabling growth of the epitaxial layer onto a foreign material with different crystal structure at the wafer-level, potentially followed by layer transfer to other beneficial substrates, which would otherwise not be possible. If successful this will enable for the first time even >10kV low cost power electronics devices, e.g. for smart grids, i.e., a high reward but the approach taken is highly speculative: (i) Do van der Waals materials survive the reactive ambient of a Ga2O3 MOCVD chamber? (ii) does potential damage to the van der Waals material impact the subsequent device quality? (iii) can we control Ga2O3's polytypes during growth? (iv) do van der Waals grown interfaces provide high enough electron and phonon transport through them, and can these be optimized or mitigated for e.g. using growth conditions or h-BN thickness, or during a layer transfer? If successful, subsequent layer transfer would allow heterogeneous integration of Ga2O3 with numerous low-cost high thermal conductivity substrates such as poly-AlN and poly-diamond to revolutionize device heat sinking. Use of p-type substrates would open the design space to bipolar devices, even superjunctions, i.e. device concepts which have transformed Si power electronics, concepts which have rarely being able to venture beyond Si, a major impact if we are successful. Lateral devices will be used to validate the effectiveness of the integration, with routes to possible commercialization of high performance devices to be explored through our industrial partnership with Dynex Semiconductor. Vertical devices (with improved power density over lateral configurations, attractive for power electronics applications) will also be demonstrated.The programme also marks a key milestone from a sustainability perspective, within a circular economy; van der Waals epitaxy or epilayer transfer used for the active devices will minimize the need for Ga2O3 substrates, to transfer to substrates with less sustainability issues (elemental Ga may become scarce within 100 years), minimizing the amount of Ga being used in power devices. Successful demonstration of heterogeneous integration of Ga2O3 by van der Waals epitaxy will also pave the way for low-cost, wafer-level integration with other ultrawide bandgap materials (e.g. single crystalline AlGaN, AlN, diamond), offering the potential to strongly reduce the contribution of inefficiency in power electronics to global energy consumption.

联合国政府间气候变化专门委员会（IPCC）在2021年8月的科学报告中称其为“人类红色代码”，强调了我们星球面临的迫在眉睫的气候风险。目前，几乎所有的能量转换电力电子设备都使用硅（Si），其效率相对较低，将能量浪费为热量。事实上，全球72%的一次能源消耗被浪费了，其中20%可以通过新的电力电子设备节省下来！使用GaN和SiC的宽带隙器件正在进入市场，但它们要么不能维持足够高的电压，要么过于昂贵，无法广泛使用，例如在智能电网中。超宽带隙氧化镓（Ga2O3）的效率远远超过窄带隙硅，已成为具有低成本和>0 -2千伏甚至10千伏电压能力的变革性竞争者，具有将功率转换效率损失大幅降低100倍的潜力。考虑到Ga2O3的高Baliga值（决定材料对功率器件的有益程度的度量），它甚至有可能超过目前的宽带隙功率器件（GaN, SiC），现在正在取代现有的Si功率电子器件，其性能超过5-10倍。在这个项目中，我们的目标是高压功率器件使用功能Ga2O3的范德华外延作为变革和革命性的载体，为低成本高压功率器件开辟一个新的研究领域。这种形式的外延使用中间层，这减少了衬底-外延层的相互作用，使得外延层在晶圆级具有不同晶体结构的外来材料上生长，潜在地随后将层转移到其他有益的衬底上，否则这是不可能的。如果成功，这将首次实现低成本电力电子设备，例如用于智能电网，即高回报，但所采取的方法是高度推测的：(i)范德华材料是否能在Ga2O3 MOCVD室的反应环境中存活？（ii）范德华材料的潜在损坏是否会影响后续的器件质量？（iii）能否在生长过程中控制Ga2O3的多型？（iv）范德华生长的界面是否提供足够高的电子和声子通过它们，这些是否可以优化或减轻，例如使用生长条件或h-BN厚度，或在层转移期间？如果成功，随后的层转移将允许Ga2O3与许多低成本高导热性衬底（如聚aln和聚金刚石）的非均质集成，从而彻底改变器件的散热。p型衬底的使用将为双极器件甚至超结打开设计空间，即已经改变了Si功率电子器件的器件概念，这些概念很少能够冒险超越Si，如果我们成功，将产生重大影响。横向器件将用于验证集成的有效性，并通过我们与Dynex半导体的工业合作伙伴关系探索高性能器件的可能商业化路线。垂直器件（比横向配置具有更高的功率密度，对电力电子应用具有吸引力）也将被展示。从循环经济的可持续性角度来看，该计划也是一个重要的里程碑；用于有源器件的范德华外延或脱皮转移将最大限度地减少对Ga2O3衬底的需求，转移到具有较少可持续性问题的衬底（元素Ga可能在100年内变得稀缺），最大限度地减少功率器件中使用的Ga量。通过范德华外延技术成功实现Ga2O3的异质集成，也将为与其他超宽带隙材料（如单晶AlGaN、AlN、金刚石）的低成本、晶圆级集成铺平道路，为大力减少电力电子器件低效率对全球能源消耗的贡献提供了潜力。