Development and Application of Non-Equilibrium Doping in Amorphous Chalcogenides

在20世纪，硅基电子产品的发展彻底改变了世界，成为现代生活背后最普遍的技术。在21世纪，人们设想技术将转向使用光（光子）与电子一起使用，或取代电子，从而大大提高信息处理的速度和数量，同时减少信息处理所需的能量。事实证明，向全光学“光子”技术的过渡是一项复杂的任务，因为电子产品所选择的材料硅在控制光的能力方面是有限的。在寻找替代材料的过程中，一类被称为非晶硫族化物（a- chgs）的玻璃显示出了非凡的前景，以至于它们被称为“光学等效硅”。硫属化合物是含有一种或多种元素硫、硒或碲为主要成分的物质。这些材料已经广泛应用于光伏、存储器（如dvd）、先进的光学设备（如激光器）和一些热电发电系统。人们普遍认为，向全光技术的转变将需要一个中间阶段，其中使用混合“光电”系统进行信息处理。这为a- chgs的发展提供了一个强有力的、令人信服的论据，因为它们可以沉积在Si上，形成一种混合方法，作为全光平台使用。虽然a-ChGs的光学性质可以被控制和修改，但在材料制备过程中修改其电子性质已被证明是极其困难的，这通常涉及在高温下熔化。在这些条件下，为了改变电子行为而添加到这些材料中的任何杂质都是无效的，因为ChG材料在熔化时能够重新排序，因此否定了期望的掺杂效果。我们已经成功地开创了一种方法，通过在a- chgs的熔化温度以下引入掺杂剂来改变它们的性质，从而不允许材料重新排序，使用离子注入。这种掺杂方法可以精确控制引入的杂质类型，并广泛应用于硅技术。由于这项工作，我们已经证明了以空间局部化的方式将大多数电荷载流子类型从空穴（p型）逆转为电子（n型）的能力。这一跨越式的成就使我们能够证明在a-ChGs中制造光学活性pn结，这将成为未来光子技术发展的使能催化剂。在这个项目中，我们将寻求在原子尺度上全面了解载流子型反转的过程，并利用这些信息对其进行优化，以及要修改的材料，从而增加进一步的功能。我们还将开发所需的先进工程方法，涉及到通过离子注入到a-ChGs中的掺杂剂的控制和激活。总之，这些将能够演示一系列光电子器件，展示构建集成光电子技术所需的关键功能。该项目将巩固英国在硫系化合物非平衡掺杂领域的世界领先地位。通过这种方式，我们将支持这些材料在全球过渡到超越CMOS技术的过程中，从而直接为知识经济的持续增长做出贡献。我们将以最先进的技术培训下一代科学家和工程师，以确保英国保持实现这一目标所需的专业知识基础，旨在确保这项工作的影响在可能的情况下最大化和加速，并广泛交流结果，包括与这项研究的所有利益相关者。

In the 20th century, the development of silicon-based electronics revolutionised the world, becoming the most pervasive technology behind modern-day life. In the 21st century, it is envisaged that technology will move to the use of light (photons) together with, or in place of, electrons, providing a dramatic increase in the speed and quantity of information processing whilst also reducing the energy required to do so. Making this transition to an all optical 'photonic' technology has proved to be a complex task, as the material of choice for electronics, silicon, is limited in its ability to control light. In the search for alternative materials, a class of glasses called amorphous chalcogenides (a-ChGs) have shown remarkable promise, to the point where they have been referred to as the 'optical equivalent of silicon'. Chalcogenides are materials which contain one or more of the elements sulfur, selenium or tellurium as a major constituent. These materials are already widely used in applications such as photovoltaics, memory (e.g. DVDs), advanced optical devices (e.g. lasers), and in some thermoelectric generation systems. It is accepted that the move to all-optical technologies will require an intermediate stage where information processing is undertaken using a hybrid 'optoelectronic' system. This provides a strong and compelling argument for the development of a-ChGs, as they can be deposited on Si to form a hybrid approach en-route to their use as an all-optical platform.Whilst the optical properties of a-ChGs may be controlled and modified it has proved to be extremely difficult to modify their electronic properties during the material preparation, which has typically involved melting at high temperatures. Any impurities that are added to these materials in order to change the electronic behaviour are ineffective under these conditions due to the ability of the ChG material to reorder itself when melted, and so negate the desired doping effect. We have successfully pioneered a method to modify their properties by introducing dopants into a-ChGs below their melting temperature, thus not allowing the material to reorder, using ion-implantation. This method of doping allows precise control of the type of impurity introduced and is widely used in silicon technologies. As a result of this work, we have demonstrated the ability to reverse the majority charge carrier type from holes (p-type) to electrons (n-type) in a spatially localised way. This step-changing achievement enabled us to demonstrate the fabrication of optically active pn-junctions in a-ChGs, which will act as the enabling catalyst for the development of future photonic technologies.In this project we will seek to develop a full understanding of the process of carrier-type reversal on the atomic scale, and use this information to optimize it, and the materials that are to be modified, so as to add further functionality. We will also develop the required advanced engineering methods which relate to the control and activation of dopants introduced using ion-implantation into a-ChGs. Together, these will enable the demonstration of a series of optoelectronic devices demonstrating the key functionalities required to build an integrated optoelectronic technology. This programme will consolidate the position of the UK as the world leader in the field of non-equilibrium doping of chalcogenides. We will, in this way, champion these materials in the world's transition to beyond CMOS technology and therefore directly contribute to the continuing growth of the knowledge economy. We will train the next generation of scientists and engineers in state-of-the-art techniques to ensure that the UK maintains the expertise base required for this purpose, aim to ensure that the impact of this work is maximised and accelerated where possible, and communicate the results widely, including to all stakeholders in this research.