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

这个小型企业创新研究第一阶段项目将解决通过氨法生长的氮化镓（GaN）的着色问题。 尽管其承诺将GaN晶片的成本降低90%，但氨生长技术存在着色问题，这阻碍了将所得衬底用于高亮度发光二极管（HB-LED）。 GaN晶片目前的主要应用是生长激光二极管（LD），其性能不会受到着色问题的严重影响。 然而，衬底中的光学损耗对于HB-LED是一个严重的问题。 该项目旨在进一步开发氨生长技术，以实现可用于HB-LED的低成本透明GaN晶片。 由于存在对氧敏感的矿化剂，因此去除作为氨氧化物块状GaN中的主要杂质的氧是这项工作中最具挑战性的方面之一。 在第一阶段项目中，我们将首先进行一系列受控实验，以揭示杂质和颜色之间的相关性。 我们还将开发一种改进的工艺，以最大限度地减少氧气污染。第一阶段项目的目标是证明这些新方法在获得透明GaN方面的可行性。该项目更广泛的影响/商业潜力是通过氨生长实现低成本透明GaN晶片，这将提高HB-LED的性能并降低成本。 GaN晶片目前的高价格不允许HB-LED与竞争产品的成本竞争力。目前氢化物气相外延（HVPE）的生产方法劳动密集，产量低，导致晶圆成本高。 由于氨生长工艺是一种可扩展的液相方法，预计将使GaN晶片成本降低90%。 低成本、透明的GaN晶片的可用性将使通过这种方法生长的衬底能够满足目前利基市场规模的十倍（2015年约10亿美元）。 目前，一些国内和国际竞争对手正在追求这一目标;然而，没有一个已经实现了适合HB-LED应用的无色GaN晶片。 我们的新工艺将直接解决矿化剂的氧化问题，我们希望这将解决着色问题。 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器背光。

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.