Free-standing wurtzite AlGaN substrates for deep ultraviolet (DUV) devices.

用于深紫外 (DUV) 器件的独立式纤锌矿 AlGaN 衬底。

• 批准号: EP/K008323/1
• 负责人: Sergei Novikov
• 金额: $ 87.72万
• 依托单位: University of Nottingham
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2013
• 资助国家: 英国
• 起止时间: 2013 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=EP%2FK008323%2F1
• 关键词: Free; standing; wurtzite; AlGaN; substrates

Ultra-violet (UV) light disinfection is one of the most promising methods for water treatment. Unlike chemical disinfection it will be fast and easy to use and will not require hazardous materials, has no danger of overdosing and does not produce toxic by-products. It has long been established that UV light can be used for air and water purification and surface decontamination. Until recently the main UV source for that application were mercury lamps. However, mercury lamps are not readily portable, are fragile, have a limited lifetime and have a disposal problem. The recent development of group III nitrides allows researchers world-wide to consider AlGaN based LEDs as a possible new alternative DUV light source. If efficient devices can be developed they will be easy to use, have potentially long life time, will not be fragile and will lend themselves to battery operation to allow their use in remote locations. Changing the composition of the active AlGaN layer, will allow one to tune easily the wavelength of the LEDs. This has stimulated active research world-wide to develop AlGaN based LEDs for air and water purification and surface decontamination. Such DUV LEDs will also have potential applications for UV solid state lighting and drug detection. The first successful semiconductor UV LEDs are now manufactured using the AlxGa1-xN material system, covering the energy range from 3.4eV (GaN) up to 6.2eV (AlN). The majority of DUV LEDs require AlxGa1-xN layers with compositions in the mid-range between AlN and GaN. For example, for efficient water purification such AlxGa1-xN LEDs need to emit in the wavelength range 250-280nm. However, there is a significant difference in the lattice parameters of GaN and AlN. One of the most severe problems hindering progress of DUV LEDs is the lack of suitable substrates on which lattice-matched AlGaN films can be grown. The consequence of a poor match is a very high defect density in the films which can impair device performance. Currently the majority of AlGaN LED devices are grown on sapphire and only rarely on expensive GaN or AlN substrates. The lattice mismatch between the substrate and the active AlGaN layer results in the poor structural quality of the layers, cracks and poor morphology of the current DUV LED devices. As a result the efficiency of the AlGaN DUV LEDs is still very low. AlxGa1-xN substrates with the proper Al content would be preferable to those of either sapphire, GaN or AlN for many ultraviolet device applications, which require active AlxGa1-xN layers with x~0.5. Bulk AlxGa1-xN substrates, which are matched in lattice constant and thermal expansion properties to epitaxial nitride layers are needed for fabrication of the highest-quality AlGaN-based DUV devices. Molecular beam epitaxy (MBE) is normally regarded as an epitaxial technique for the growth of very thin layers with monolayer control of their thickness. However, we have recently successfully used the plasma-assisted molecular beam epitaxy (PA-MBE) technique for bulk crystal growth and we produced free-standing layers of metastable zinc-blende (cubic) GaN up to 100 microns in thickness. We have demonstrated the scalability of the process by growing free-standing zinc-blende GaN layers up to 3-inches in diameter.The main aims of this project are the growth of free-standing wurzite AlGaN substrates by MBE, comprehensive analysis of their structural, optical and transport properties and MOVPE development of the first DUV AlGaN LEDs on AlGaN substrates. This is the first step towards developing commercially viable production of high efficient DUV LEDs on AlGaN substrates.Growth of free-standing wurzite AlGaN substrates by MBE will be carried out at Nottingham. MOVPE growth and testing of DUV LED epitaxial layers will be carried out at Cambridge. The fabrication and subsequent characterisation of DUV LEDs will be carried out at Bath.

紫外线（UV）光消毒是最有前途的水处理方法之一。与化学消毒不同的是，它将是快速和易于使用的，不需要危险材料，没有过量的危险，也不会产生有毒的副产品。长期以来，人们已经确定紫外线可以用于空气和水的净化以及表面去污。直到最近，该应用的主要紫外线源是汞灯。然而，汞灯不容易携带，易碎，寿命有限，并且存在处置问题。第三族氮化物的最新发展使世界各地的研究人员能够考虑将基于AlGaN的LED作为可能的新替代DUV光源。如果能够开发出高效的设备，它们将易于使用，具有潜在的长寿命，不会易碎，并且将适合电池操作，以允许它们在偏远地区使用。改变有源AlGaN层的组成将允许人们容易地调谐LED的波长。这刺激了世界范围内的积极研究，以开发用于空气和水净化以及表面去污的基于AlGaN的LED。这种DUV LED也将具有用于UV固态照明和药物检测的潜在应用。第一个成功的半导体UV LED现在使用AlxGa 1-xN材料系统制造，覆盖从3.4eV（GaN）到6.2eV（AlN）的能量范围。大多数DUV LED需要AlxGa 1-xN层，其成分介于AlN和GaN之间。例如，为了有效的水净化，这种AlxGa 1-xN LED需要在250- 280 nm的波长范围内发射。然而，GaN和AlN的晶格参数存在显著差异。阻碍深紫外LED发展的最严重问题之一是缺乏合适的衬底，在其上可以生长晶格匹配的AlGaN膜。差匹配的结果是膜中非常高的缺陷密度，这会损害器件性能。目前，大多数AlGaN LED器件都生长在蓝宝石上，很少生长在昂贵的GaN或AlN衬底上。衬底和有源AlGaN层之间的晶格失配导致层的差的结构质量、裂缝和当前DUV LED器件的差的形态。结果，AlGaN DUV LED的效率仍然非常低。具有适当Al含量的AlxGa 1-xN衬底对于许多紫外器件应用将优于蓝宝石、GaN或AlN衬底，这些紫外器件应用需要x~0.5的有源AlxGa 1-xN层。体AlxGa 1-xN衬底，这是匹配的晶格常数和热膨胀性能的外延氮化物层需要用于制造最高质量的AlGaN基DUV器件。分子束外延（MBE）通常被认为是一种用于生长非常薄的层的外延技术，其厚度由单层控制。然而，我们最近已经成功地使用等离子体辅助分子束外延（PA-MBE）技术的块状晶体生长，我们产生了独立的亚稳态锌-立方（立方）GaN层的厚度高达100微米。我们已经通过生长直径达3英寸的自支撑锌掺杂GaN层展示了该工艺的可扩展性。该项目的主要目标是通过MBE生长自支撑纤锌矿AlGaN衬底，全面分析其结构，光学和输运特性，并在AlGaN衬底上MOVPE开发第一个DUV AlGaN LED。这是在AlGaN衬底上开发商业上可行的高效深紫外LED生产的第一步。诺丁汉将通过分子束外延生长独立的纤锌矿AlGaN衬底。深紫外LED外延层的MOVPE生长和测试将在剑桥进行。DUV LED的制造和随后的表征将在巴斯进行。

项目成果

Investigation of the GaN-on-GaAs interface for vertical power device applications

• DOI: 10.1063/1.4887139
• 发表时间: 2014-07
• 期刊: Journal of Applied Physics
• 影响因子: 3.2
• 作者: J. Möreke;M. Uren;S. Novikov;C. T. Foxon;S. H. Vajargah;D. Wallis;C. Humphreys;S. Haigh;A. Al-Khalidi;E. Wasige;I. Thayne;M. Kuball

Molecular beam epitaxy of free-standing bulk wurtzite Al x Ga 1-x N layers using a highly efficient RF plasma source

使用高效 RF 等离子体源对独立式块体纤锌矿 Al x Ga 1-x N 层进行分子束外延

• DOI: 10.1002/pssc.201510166
• 发表时间: 2016
• 期刊: physica status solidi c
• 作者: Novikov S

Doping of free-standing zinc-blende GaN layers grown by molecular beam epitaxy

通过分子束外延生长的独立式闪锌矿 GaN 层的掺杂

• DOI: 10.1016/j.jcrysgro.2014.06.014
• 发表时间: 2014
• 期刊: Journal of Crystal Growth
• 影响因子: 1.8
• 作者: Novikov S

Study of confined coherent acoustic phonon modes in a free-standing cubic GaN membrane by femtosecond spectroscopy

• DOI: 10.1063/1.4931495
• 发表时间: 2015-09
• 期刊: Applied Physics Letters
• 影响因子: 4
• 作者: Chuan He;M. Grossmann;D. Brick;M. Schubert;S. Novikov;C. T. Foxon;V. Gusev;A. Kent;T. Dekorsy

Polarized infrared reflectance study of free standing cubic GaN grown by molecular beam epitaxy

• DOI: 10.1016/j.matchemphys.2014.03.008
• 发表时间: 2014-07
• 期刊: Materials Chemistry and Physics
• 影响因子: 4.6
• 作者: S. C. Lee;S. Ng;H. A. Hassan;Z. Hassan;N. Zainal;S. Novikov;C. T. Foxon;A. Kent