Heterogeneous semiconductors: epitaxy and electronic properties

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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.