STTR Phase I: Nonpolar GaN-Based Light Emitting Diodes

这个小型企业技术转移（STTR）一期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）。非极性氮化镓基led将立即应用于要求苛刻的下一代固态照明应用。近年来，利用氮化镓（GaN）半导体的发光二极管（led）的性能有了显著的提高。然而，这些传统led的生长和制造的关键限制将最终阻止它们被最苛刻的照明应用所采用。商业gan基led是在不匹配的衬底上制造的，包括蓝宝石和碳化硅。所得的GaN器件薄膜包含高位错密度（109 /cm2）和/或裂纹密度，通常需要复杂的器件加工。此外，几乎所有氮化镓基led都是由极性c平面氮化镓薄膜制成的。这类装置的内置偏振场会降低载流子重组效率，从而限制光输出。研究小组已经制造出了基于gan的非极性led，这种led没有内置的极化场。它们固有地具有更高的内部量子效率，因此比传统的c-平面led具有更高的输出功率。该公司提出了一项研究工作，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）蓝色和绿色GaN基led。公司团队将开发高质量的非极性氮化镓“模板”层，而研究团队将进行LED的生长、制造和测试。在商业上，非极性氮化镓基led未来最大的应用是取代传统的白光光源，如荧光灯。固态白光可以通过分立红色、绿色和蓝色led的组合来实现；另外，短波长（如蓝色、紫外线）氮化led可以激发荧光粉混合物。在任何一种情况下，led必须具有足够低的成本和高输出功率，以证明替代传统灯是合理的。非极性氮化镓基led将满足最苛刻的照明要求，而传统的极性氮化镓基led则不能。此外，由于非极性氮化镓基led发射偏振光，液晶显示背光等应用将大大受益于它们的采用。

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.