Study of semi-polar and non-polar nitride based structures for opto-electronic device applications

用于光电器件应用的半极性和非极性氮化物基结构的研究

基本信息

批准号：
EP/J001627/1
负责人：
Philip Dawson
金额：
$ 49.4万
依托单位：
University of Manchester
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2011
资助国家：
英国
起止时间：
2011 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=EP%2FJ001627%2F1
关键词：
Study semi polar non nitride

项目摘要

Over the last 10 years gallium nitride based light emitting diodes (LEDs) have found widespread use as the active light emitting element of various optical displays, ranging from traffic lights to large area displays in, for example, sports stadia. This revolution in display technology has occurred because gallium nitride LEDs have not only the ability to generate blue and green light but also very efficiently, both of these attributes were not previously possible with other types of LED. Despite this revolutionary leap forward in display technology gallium nitride LEDs offer still further opportunities of developing not only even more efficient displays that can be used in televisions but also very efficient lighting systems, so called Solid State Lighting (SSL).At the heart of most modern televisions is a liquid crystal display unit that is capable of displaying today's high definition programs. The liquid crystal display works by either transmitting or absorbing light when an electrical signal is applied to the crystal. For this to occur the light that is shone from the back of the crystal towards the viewer has to be polarised in a particular direction, i.e. the maxima and minima that make up the light wave light lie in a particular direction. Conventional light sources, including the latest generation of LED, emit unpolarised light so to make the light suitable for use in a liquid crystal based television means that the light has to be passed through a light polariser thus rejecting approximately 50% of the emitted light. Clearly this is an inefficient system and the overall efficiency of television displays would be greatly improved if an efficient light source could emit polarised light. By growing the nitride based LEDs on new forms of template, so-called semi-polar and non-polar crystals, it is possible to fabricate polarised light sources offering us the possibility of significant energy savings. At the moment the fundamental scientific questions that govern not only how well the light is polarised but also efficiency of the light generation process are not understood. In this program we will investigate these issues by making a comprehensive study of both the materials and underlying physics that will enable the fabrication of a new generation of liquid crystal based displays for inclusion in low power consumption televisions.SSL is viewed as the most likely replacement for incandescent light bulbs and the current generation of compact fluorescent lamps. From this application alone the scale of the potential for energy saving can be judged by the following: "By 2025, SSL could reduce the global amount of electricity used for lighting by 50%. In the US alone this would alleviate the need for 133 new power stations (1000 MW each), eliminate 255 million metric tons of CO2 and save $115 billion of electricity costs." (The Promise of Solid State Lighting for General Illumination, US Department of Energy, 2000). The basis for SSL systems is that white light can produced by either using the combined output of a blue light emitting LED and a yellow light emitting phosphor or be combining the output from blue, green and red light emitting LEDs. The highest light generation efficiency achieved so far is ~70%, while in its self is a remarkably high figure for SSL to be employed in our offices requires efficiencies approaching ~90%. This step forward has so far proved impossible and it is widely believed that this is due to intrinsic reductions in the rate of light emission caused by internal electric fields. These fields can be reduced or eliminated by the growth of LEDs on semi-polar or non-polar templates. The promise of highly efficient LEDs using this methodology remains unfulfilled principally due to the difficulties of growing crystals of the required quality. We anticipate by using novel and improved methods of crystal growth that these problems can be overcome allowing the promise of SSL to be fulfilled.

在过去的十年中，基于氮化炮的光发射二极管（LED）发现广泛用作各种光学显示的主动发光元件，从交通信号灯到大面积显示，例如体育体育场。这场展示技术的革命之所以发生，是因为氮化炮不仅具有产生蓝光和绿光的能力，而且还非常有效，其他类型的LED都无法实现这两种属性。尽管在展示技术中进行了这种革命性的飞跃，但硝酸盐LED却提供了进一步的机会，不仅可以在电视中使用更有效的显示器，而且还提供了非常有效的照明系统，所谓的固态照明（SSL）是大多数现代电视的心脏。当将电信号施加到晶体上时，液晶显示器可以通过传输或吸收光线作用。为此，要发生从晶体的背面照射到观看者的光，必须朝着特定方向偏振，即构成光波光的最大值和最小值位于特定方向。传统的光源，包括最新一代LED，发出非极化光，以使适合在液晶电视中使用的光意味着必须通过光偏光仪，从而拒绝了大约50％的发光光。显然，这是一个效率低下的系统，如果有效的光源可以发出偏振光，电视显示的总体效率将大大提高。通过将基于氮化物的LED种植在新形式的模板，所谓的半极和非极性晶体上，可以制造偏振光来源，从而为我们提供大量节能的可能性。目前，基本的科学问题不仅控制着光的两极分化，而且还不了解光发过程的效率。在该计划中，我们将通过对材料和基础物理学进行全面研究来调查这些问题，这些物理和基础物理学将能够制造新一代的基于液晶的显示器，以包含在低功耗电视中。SSSL被视为最有可能替代白炽灯灯泡和当前紧凑型荧光灯的灯泡。仅此应用程序就可以通过以下判断来判断节能的可能性：“到2025年，SSL可以将用于照明的全球电力减少50％。仅在美国，这将减轻133个新电力站（每个1000 MW）的需求（每个1000 MW），消除2.55亿吨的CO2和1,150亿美元的电力成本。” （美国能源部固态照明对一般照明的承诺，2000年）。 SSL系统的基础是，通过使用蓝光发射LED的组合输出和发出黄光发出磷光器的组合输出可以产生白光，或者将蓝色，绿色和红光发射LED的输出结合在一起。到目前为止，达到的最高光发电效率是〜70％，而在自我中，在我们的办公室中使用SSL的数字非常高，需要接近90％的效率。迄今为止，这一前进是不可能的，人们普遍认为这是由于内部电场引起的光发射速率的内在降低所致。通过在半极或非极性模板上LED的生长可以减少或消除这些磁场。使用这种方法的高效LED的承诺主要是由于所需质量的晶体的困难，这主要是无法实现的。我们可以通过使用新颖和改进的晶体生长方法来克服这些问题，从而实现SSL的承诺。