STTR Phase I: Nonpolar GaN-Based Light Emitting Diodes

这个小型企业技术转移(STTR)第一阶段项目将开发具有高能效和输出功率的非极性氮化镓(GaN)基发光二极管(LED)。非极性GaN基LED将立即应用于要求苛刻的下一代固态照明应用。最近，使用氮化镓(GaN)半导体的发光二极管(LED)的性能有了显着的改善。然而，这些传统LED在生长和制造方面的关键限制最终将阻止它们应用于要求最苛刻的照明应用。商用GaN基LED是在不匹配的衬底上制造的，包括蓝宝石和碳化硅。得到的GaN器件薄膜含有高的位错密度(109/cm2)和/或裂纹密度，通常需要复杂的器件处理。此外，几乎所有的GaN基LED都是由极性的c平面GaN薄膜制成的。这种设备受到内置偏振场的影响，这些场降低了载流子复合效率，从而限制了光输出。研究小组已经制造了非极性的GaN基LED，这种LED没有内置的偏振场。与传统的c平面LED相比，它们具有更高的内部量子效率，因此输出功率也更高。该公司提出了一项研究工作，即在具有均匀低扩展缺陷密度的非极性GaN薄膜上生长和制造高亮度非极性(m面和a面)蓝绿GaN基LED。该公司团队将生长高质量的非极性GaN‘模板’层，而研究团队将进行LED的生长、制造和测试。在商业上，非极性GaN基LED未来最大的应用是取代传统的白色光源，如荧光灯。固态白色照明可以通过离散的红、绿和蓝LED的组合来实现；或者，短波长(例如蓝色、紫外线)氮化物LED可以激发混合磷光体。在任何一种情况下，LED必须具有足够低的成本和足够高的输出功率，以证明更换传统灯具是合理的。非极性GaN基LED将满足最苛刻的照明要求，而传统的极性GaN基LED则不能。此外，由于非极性GaN基LED发射偏振光，采用它们将极大地受益于液晶显示器背光等应用。

This Small Business Technology Transfer (STTR) Phase I project will develop nonpolar gallium nitride (GaN)-based light emitting diodes (LEDs) with high energy efficiency and output power. Nonpolar GaN-based LEDs will find immediate application in demanding next-generation solid-state lighting applications. Recently there has been significant improvement in the performance of light emitting diodes (LEDs) utilizing gallium nitride (GaN) semiconductors. However, key limitations in the growth and fabrication of these conventional LEDs will ultimately prevent their adoption for the most demanding lighting applications. Commercial GaN-based LEDs are fabricated on ill-matched substrates including sapphire and silicon carbide. The resulting GaN device films contain high dislocation densities ( 109 /cm2) and/or crack densities, often requiring complicated device processing. Additionally, nearly all GaN-based LEDs have been fabricated from polar c-plane GaN thin films. Such devices suffer from built-in polarization fields that reduce carrier recombination efficiency and thus limit light output. Research groups have fabricated nonpolar GaN-based LEDs, which have no built-in polarization fields. They have inherently higher internal quantum efficiency and thus higher output power than conventional c-plane LEDs. The company proposes a research effort to grow and fabricate high-brightness nonpolar (m-plane and a-plane) blue and green GaN-based LEDs on nonpolar GaN films with uniformly low extended defect density. The company team will grow high-quality nonpolar GaN 'template' layers, while the research team will perform LED growth, fabrication, and testing. Commercially, the largest future application for nonpolar GaN-based LEDs is replacement of conventional white light sources such as fluorescent bulbs. Solid-state white lighting may be achieved via combinations of discrete red, green, and blue LEDs; alternately, short-wavelength (e.g. blue, ultraviolet) nitride LEDs can excite phosphor mixtures. In either case, the LEDs must have sufficiently low cost and high output power to justify replacement of conventional lamps. Nonpolar GaN-based LEDs will meet the most demanding lighting requirements, whereas conventional polar GaN-based LEDs cannot. Additionally, since nonpolar GaN-based LEDs emit polarized light, applications such as liquid crystal display backlighting will greatly benefit from their adoption.