Heterogeneous semiconductors: epitaxy and electronic properties

在这项建议中，我们重点讨论了异质磁性半导体(MSC)的气相外延(VPE)，例如含GaP的MnP纳米团簇，以及基于III-V化合物的量子异质结构(QHS)。我们的主要兴趣是了解(I)我们生长的材料的固有结构与光学、磁性和传输性质之间的关系，以及(Ii)这种结构是如何受生长过程控制的。最近已经确定，含有磁性材料纳米团簇的非均相MSC外延层的磁性取决于纳米团簇夹杂物的尺寸、晶体结构和取向，并且已经建立了从我们生长的样品中提取这些信息的方案。然而，关于这些夹杂物从气相生长时如何控制夹杂物的加入，人们知之甚少。因此，我们的目标之一是通过精心设计的生长实验和详细的材料表征来建立控制结构的基本机制。这也适用于我们正在进行的应变QHS的研究，包括应变层超晶格和层叠的相干量子点层，我们将在其中加入新的稀氮化物用于红外光探测，以及具有纳米夹杂的薄膜用于热电研究。我们将在我们的实验室中生长这些异质半导体，为此，我们有两个专用的金属有机VPE反应器，在那里我们可以生长磷化物、砷化物、锑化物和稀氮化物。我们将自己或通过多年发展和维护的成熟的合作者网络来充分描述外延层的特征。特别是，载流子在许多异质半导体中的寿命几乎没有受到关注，但它们将被用于各种设备中。拟议的大部分工作是与先进材料和器件有关的基础性工作，预计将有助于建立进一步推进应用所需的基本理解，例如设计用于能量转换和节能、光子探测和光学隔离的创新器件。

In this proposal we focus on the vapor phase epitaxy (VPE) of heterogeneous magnetic semiconductors (MSC), such as GaP containig nanoclusters of MnP, and of quantum heterostructures (QHS) based on III-V compounds. Our main interests are to understand (i) the relationship between the inherent structure and the optical, magnetic and transport properties of the materials we grow, and (ii) how this structure is governed by the growth processes. It has recently been determined that the magnetic properties of heterogeneous MSC epilayers containing nanoclusters of magnetic materials depend on the size, crystallographic structure and orientation of the nanocluster inclusions, and protocols have been established to extract this information from the samples we grow. Yet, little is known on how to control the incorporation of these inclusions when growing from the vapor phase. Thus, one of our objectives is to establish the basic mechanisms controlling the structure by carefully designed growth experiments followed by detailed material characterization. This also applies to our ongoing study of strained QHS, including strained-layer supperlattices and stacks of layers of coherent quantum dots to which we will incorporate new dilute nitride for applications in IR photo detection, and films with nanometric inclusions for thermoelectric studies. We will grow these heterogeneous semiconductors in our laboratory, and for this purpose we have two dedicated metal organic VPE reactors where we can grow phosphides, arsenides, antimonides and dilute nitrides. We will fully characterize the epilayers ourselves or through a well established network of collaborators developed and maintained through many years. In particular, the carriers' lifetimes in many of these heterogeneous semiconductors have received little attention, yet they will be needed for applications in a variety of devices. Most of the work proposed is of a fundamental nature related to advanced materials, and devices, and it is expected to help establish the basic understanding needed for further advances in applications, such as the design of innovative devices for energy conversion and energy conservation, photon detection and optical isolation.