SBIR Phase I: Realization of Transparent Gallium Nitride Wafers by Ammonothermal Growth

这个小企业创新研究一期项目将解决氨热法生长的氮化镓（GaN）的着色问题。尽管氨热生长技术有望将GaN晶圆的成本降低90%，但它存在着显色问题，这阻碍了高亮度发光二极管（hb - led）衬底的使用。目前氮化镓晶圆的主要应用是生长激光二极管（ld），其性能不受显色问题的严重影响。然而，基板中的光学损耗是hb - led的一个严重问题。该项目旨在进一步发展氨热生长技术，以实现可用于hb - led的低成本，透明的GaN晶圆。氧是氨热体氮化镓的主要杂质，由于存在氧敏感矿化剂，因此去除氧是这项工作中最具挑战性的方面之一。在一期项目中，我们将首先进行控制组实验，以揭示杂质与颜色之间的相关性。我们还将开发一种改进的工艺，以尽量减少氧气污染。第一阶段项目的目标是证明这些新方法在获得透明氮化镓方面的可行性。该项目的更广泛的影响/商业潜力是通过氨热生长实现低成本，透明的GaN晶圆，这将提高hb - led的性能并降低成本。目前氮化镓晶圆的高价格不允许hb - led与竞争产品的成本竞争力。目前的氢化物气相外延（HVPE）生产方法劳动密集，产量低，导致晶圆成本高。由于氨热生长法是一种可扩展的液相法，因此有望将GaN晶圆成本降低90%。低成本、透明的氮化镓晶圆的可用性将允许通过这种方法生长衬底，以满足市场规模是当前利基市场的十倍（2015年约为10亿美元）。目前，国内外几家竞争对手都在追求这一目标；然而，目前还没有实现适合HB-LED应用的无色GaN晶圆。我们的新工艺将直接解决矿化剂的氧化问题，我们预计，这将解决着色问题。该项目将有助于实现低成本hb - led，不仅用于节能固态照明产品，而且用于汽车前照灯和显示背光。

This Small Business Innovation Research Phase I project will address the coloration problem of gallium nitride (GaN) grown by the ammonothermal method. Despite its promise to reduce the cost of GaN wafers by 90%, the ammonothermal growth technique has a coloration problem which impedes the use of the resulting substrates for high-brightness light emitting diodes (HB-LEDs). The current major application of GaN wafers is for growing laser diodes (LDs), for which performance is not seriously affected by the coloration issue. However, optical loss in the substrate is a serious issue for HB-LEDs. This project aims to further develop the ammonothermal growth technology to realize low-cost, transparent GaN wafers usable for HB-LEDs. Removing oxygen, which is the primary impurity in ammonothermal bulk GaN, is one of the most challenging aspects of this effort because of the presence of oxygen-sensitive mineralizers. In the Phase I project, we will first conduct controlled sets of experiments to reveal the correlation between impurities and coloration. We will also develop an improved process to minimize the oxygen contamination. The goal of the Phase I project is to prove the feasibility of these new approaches in obtaining transparent GaN.The broader impact/commercial potential of this project is the realization of low-cost, transparent GaN wafers via ammonothermal growth, which will improve the performance and reduce the cost of HB-LEDs. The current high price of GaN wafers does not permit cost competitiveness of HB-LEDs with competing products. The high wafer cost is attributed to the current labor-intensive, low-yield production method of hydride vapor phase epitaxy (HVPE). Since the ammonothermal growth process is a scalable liquid-phase method, it is expected to reduce GaN wafer cost by 90%. The availability of low-cost, transparent GaN wafers will permit substrates grown via this method to address a market which is ten times the size of the current niche (~$1 billion in 2015). Currently, several domestic and international competitors are pursuing this goal; however, none has achieved colorless GaN wafers suitable for the HB-LED application. Our novel processes will directly address the oxidation problem of mineralizers which, we expect, will solve the coloration problem. This project will contribute to realization of low-cost HB-LEDs not only for energy-efficient solid-state lighting products, but also for automobile headlamps and display backlights.