Growth and Electronic Properties of InN and N-rich Alloys

本项目将研究一种新的光电半导体材料--氮化铟(InN)的生长和特性。从组成材料单个原子层的最初几个原子的沉积开始，将使用扫描隧道显微镜(STM)观察生长，直到形成完整的单分子层，再到薄膜的生长(即几微米厚)。这种材料在技术上很重要，因为直到2002年底，人们还认为Inn的带隙能量为1.9 eV。然而，在2002年，高质量的InN薄膜首次被生长出来，并且这种材料被发现具有0.7 eV的带隙能量(即在红外区)。这一发现意味着重新评估这种材料及其合金的所有基本性质(即结构、光学和电子性质)是很重要的。这在技术上的重要原因是，现在，利用这种较低的带隙能量，InN可以与宽禁带材料GaN(带隙为3.4 eV/即紫外区)结合形成InGaN。因此，将有可能制造一整套新设备，包括覆盖整个太阳光谱的一系列高效率太阳能电池，以及在太赫兹波段工作的高频设备，而不必结合几种不同的半导体材料，以及与这一复杂工艺相关的所有问题。由于我们之前发现的一系列与纯InN相关的固有性质(表面电子积累和p型掺杂困难)，我们将开发一系列这种材料的新型合金，包括镓(Ga)和砷(As)。为此，我们将仔细研究这些材料是如何生长的(确切地说，是逐层原子层)，以及薄膜的基本性质随着Ga和As含量的变化而改善，从而实现一系列新的光学和电子设备应用。

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.