Beyond modulation doping

超越调制掺杂

• 批准号: EP/J003417/1
• 负责人: David Ritchie
• 金额: $ 109.4万
• 依托单位: University of Cambridge
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2012
• 资助国家: 英国
• 起止时间: 2012 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=EP%2FJ003417%2F1
• 关键词: Beyond; modulation; doping

When an impurity atom in a semiconductor crystal has more (or fewer) valence electrons than the atom it replaces, it can donate one or more electrons to (or accept them from) the crystal lattice. The deliberate addition of such impurities, called dopants, is the traditional means of generating mobile charge carriers (negatively-charged electrons or positively-charged holes) within semiconductor devices, including the silicon-based metal-oxide-semiconductor field-effect transistors (MOSFETs) and compound semiconductor high-electron-mobility transistors (HEMTs) ubiquitous in modern electronics.High-mobility, gallium-arsenide-based HEMTs in particular, which can be made from ultrahigh-purity wafers grown by molecular beam epitaxy (MBE), have also been instrumental in the discoveries of new physics, including the fractional quantum Hall (FQH) effect, microwave-induced resistance oscillations, Wigner solid phases in magnetic field, ballistic transport and conductance quantisation in one-dimensional channels, single-electron quantum dots, Kondo physics, spin-based solid-state qubits, possible excitonic superfluidity in double-quantum-well structures, and possible non-Abelian statistics in certain novel FQH states.Even with the technique of modulation doping, where dopants are placed far away from the conducting channel, disorder due to the ionised dopants can still be felt by the carriers in a high-purity wafer, and this disorder can interfere with phenomena being studied. However, these intentional dopants are not necessary if one uses instead an external electric field to electrostatically induce a two-dimensional electron gas (2DEG) or hole gas (2DHG) at the semiconductor heterointerface. This electric field can be applied with electrostatic gates on the front and/or back side of devices. Although the proof-of-principle demonstration of undoped devices (which required only one working device) was reported more than eighteen years ago by Bell Labs (USA), the complex cleanroom fabrication process and the ensuing very low yield of working devices have prevented the use of undoped devices from becoming mainstream. Over the last three years, our group has made a number of technological breakthroughs which allow a 90+% yield of working devices, including Hall bars and nanostructures (e.g., quantum dots). This yield is now high enough to have research projects depend on a steady, reliable supply of high-quality samples.To capitalise on this success, we propose to combine our ability to fabricate such devices on demand with our expertise in MBE semiconductor wafer growth and millikelvin temperature measurements to further progress on two of the topics listed above, the fractional quantum hall effect and spin-based solid-state qubits. Many "exotic" FQH states present in the second Landau level do not fit the Laughlin/Jain theory which describes "conventional" FQH states, and are particularly sensitive to dopant-induced disorder. Our experimental programme will shed light on the nature of these states, particularly the famous state at filling factor 5/2 and its possible non-Abelian properties. Gate-defined electron spin qubits in GaAs were once amongst the forerunner systems for the realisation of a quantum computer. However, this system suffers from the presence of hyperfine interactions and charge noise, both of which cause spin decoherence on timescales too short for a practical quantum computer. Our experimental programme will demonstrate how both hyperfine interactions and charge noise are significantly reduced when gate-defined double quantum dots are fabricated from undoped 2DHGs.Our proposed work will yield fundamental insights into physical phenomena not easily accessible using even the highest quality doped heterostructures.

当半导体晶体中的杂质原子具有替代原子的价值（或更少）的价电子时，它可以将一个或多个电子捐赠给（或从中接受）晶体晶格。在半导体设备中产生移动电荷载体（带负电荷的电子或正负电荷的）的传统手段，包括基于硅的金属氧化物 - 氧化物 - 氧化物 - 氧化物 - 官方效应转换器（MOSF）和混合半径式透射式（混合半径式横向器）（包括基于硅的金属氧化物），是在半导体设备中产生移动电荷载体（带负电荷的电子或正负孔）的传统手段，并结合了半导体高 - 电气 - 电源透射器（包括基于硅） electronics.High-mobility, gallium-arsenide-based HEMTs in particular, which can be made from ultrahigh-purity wafers grown by molecular beam epitaxy (MBE), have also been instrumental in the discoveries of new physics, including the fractional quantum Hall (FQH) effect, microwave-induced resistance oscillations, Wigner solid phases in magnetic field, ballistic transport and conductance quantisation in一维通道，单电子量子点，物理学，基于自旋的固态量子量，可能的双量子孔结构中可能的激发性超流体以及某些新型FQH状态的非阿布尔统计数据，即使在调制掺杂方面，也可以通过在该掺杂剂的范围内降低了型号的范围。高纯度晶圆，这种疾病可能会干扰正在研究的现象。但是，如果一个人使用外部电场来静电诱导二维电子气体（2DEG）或半导体异源面部孔（2DHG），则无需这些故意的掺杂剂。该电场可以在设备的前部和/或背面使用静电门施加。尽管贝尔实验室（Bell Labs（USA））在18年前报告了未蛋白设备的原则证明（仅需要一种工作设备），但复杂的洁净室制造过程以及随之而来的工作设备的非常低的收益却阻止了使用未覆盖的设备成为主流的使用。在过去的三年中，我们的小组取得了许多技术突破，允许工作设备的收率达到90％+％，包括霍尔杆和纳米结构（例如量子点）。现在，这种产量足够高，可以使研究项目取决于稳定，可靠的高质量样品供应。要利用这一成功，我们建议将我们在需求中制造此类设备的能力与我们在MBE半导体晶圆增长和Millikelvin温度测量中的专业知识相结合，以进一步列出了上述主题的进一步进展，以上列出了固定量和基于Spinum Hall效应效果。第二个兰道级存在的许多“异国” FQH国家不符合描述“常规” FQH状态的Laughlin/Jain理论，并且对掺杂剂诱导的疾病特别敏感。我们的实验计划将阐明这些状态的性质，尤其是在填充因子5/2及其可能的非亚伯属性的著名状态。 GAAS中的栅极定义的电子自旋量值曾经是实现量子计算机的先驱系统之一。但是，该系统遭受了超精细相互作用和电荷噪声的存在，这两者都会在时间尺度上导致旋转的分解，对于实用的量子计算机而言太短。我们的实验计划将证明，当栅极定义的双量子点是用未居住的2DHG制造时，超精细相互作用和电荷噪声如何显着降低。我们所提出的工作将产生对物理现象的基本见解，即使是使用最高质量的掺杂异掺杂的异质结构也无法轻易访问的物理现象。

项目成果

Non-invasive charge detection in surface-acoustic-wave-defined dynamic quantum dots

表面声波定义的动态量子点中的非侵入式电荷检测

• DOI: 10.1063/1.4966667
• 发表时间: 2016
• 期刊: Applied Physics Letters
• 影响因子: 4
• 作者: Astley M

Thermal dissociation of free and acceptor-bound positive trions from magnetophotoluminescence studies of high quality GaAs / Al x Ga 1 - x As quantum wells

高质量 GaAs / Al x Ga 1 - x As 量子阱的磁光致发光研究中游离和受主结合的正三重子的热解离

• DOI: 10.1103/physrevb.93.165303
• 发表时间: 2016
• 期刊: Physical Review B
• 影响因子: 3.7
• 作者: Bryja L

Determining energy relaxation length scales in two-dimensional electron gases

确定二维电子气中的能量弛豫长度尺度

• DOI: 10.1063/1.4926338
• 发表时间: 2015
• 期刊: Applied Physics Letters
• 影响因子: 4
• 作者: Billiald J

Growth variations and scattering mechanisms in metamorphic In0.75Ga0.25As/In0.75 Al0.25As quantum wells grown by molecular beam epitaxy

分子束外延生长变质In0.75Ga0.25As/In0.75 Al0.25As量子阱的生长变化和散射机制

• DOI: 10.1016/j.jcrysgro.2015.02.038
• 发表时间: 2015
• 期刊: Journal of Crystal Growth
• 影响因子: 1.8
• 作者: Chen C

Quantized escape and formation of edge channels at high Landau levels and edge transport mediated zero-differential resistance states

高朗道水平下的量子逃逸和边缘通道的形成以及边缘传输介导的零微分电阻状态

• DOI: 10.1103/physrevb.90.045301
• 发表时间: 2014
• 期刊: Physical Review B
• 影响因子: 3.7
• 作者: Chepelianskii A