Growth and Electronic Properties of InN and N-rich Alloys

本项目将研究一种新型光电半导体材料，即氮化铟（InN）的生长和表征。从构成材料单个原子层的前几个原子的沉积开始，将使用扫描隧道显微镜（STM）观察生长，直到完整单层的发展，并一直到薄膜的生长（即几微米厚）。这种材料在技术上很重要，因为直到2002年底，人们认为InN的带隙能量为1.9 eV。然而，在2002年，高质量的InN薄膜首次被生长，并且发现这种材料具有0.7 eV的带隙能量（即在红外线）。这一发现意味着重新评估这种材料及其合金的所有基本特性（即结构，光学和电子特性）非常重要。其技术上重要的原因是，现在，利用这种较低的带隙能量，InN可以与宽带隙材料GaN（带隙为3.4 eV /即在紫外线中）组合以形成InGaN。因此，将有可能制造一系列新设备，包括一系列跨越整个太阳光谱的高效太阳能电池，以及在THz波段工作的高频设备，而不必将几种不同的半导体材料联合收割机与复杂工艺中的所有问题结合起来。由于我们先前发现的与纯InN相关的一系列固有特性（表面电子积累和p型掺杂的困难），我们将开发一系列这种材料与镓（Ga）和砷（As）的新型合金。我们将通过仔细研究这些材料如何生长（确切地说是原子层的原子层）以及薄膜的基本性质如何改善来实现这一点，作为Ga和As含量的函数，从而实现一系列新的光学和电子器件应用。

This project will study the growth and characterisation of a new optoelectronic semiconductor material, namely indium nitride (InN). Starting from the deposition of the first few atoms that make up a single atomic layer of the material, the growth will be observed using scanning tunnelling microscopy (STM), through to the development of complete monolayers, and all the way to the growth of thin films (i.e. several microns thick). This material is important technologically because up until late 2002, it was thought that InN had a band-gap energy of 1.9 eV. However, in 2002, high quality InN thin films were grown for the first time and this material was found to have a band-gap energy of 0.7 eV (i.e. in the infra-red). This discovery has meant that it is important to re-assess all of the fundamental properties (i.e. structural, optical and electronic properties) of this material and its alloys. The technologically important reason for this is that now, with this lower band-gap energy, InN can be combined with the wide-gap material GaN (band gap of 3.4 eV / i.e. in the ultra-violet) to form InGaN. It will therefore be possible to make a whole range of new devices, including a range of high efficiency solar cells spanning the entire solar spectrum, and high frequency devices that operate in the THz band, without having to combine several different semiconductor materials, with all the problems that go with that complex process. Because of a range of inherent properties associated with pure InN (surface electron accumulation and difficulty with p-type doping) which we have previously discovered, we will develop a range of novel alloys of this material with both gallium (Ga) and arsenic (As). We will do this by carefully examining how these materials grow (quite literally atomic layer-by-atomic layer) and what fundamental properties of the thin films improve, as a function of Ga and As content, enabling a whole range of new optical and electronic device applications.