Bandgap and wavefunction engineering of semiconductor heterostructures

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Materials such as magnetic semiconductor (MS) alloys, and quantum heterostructures (QHS) such as embedded quantum dots (QDs) play an important role in spintronic and photonic applications, and  are becoming essential for technological innovation. My proposal will focus on (1) the epitaxial growth of QHS and MS alloys and (2) their characterization and application in discrete devices. We will continue our ongoing study of strained III-V compound QHS, which includes stacks of multiple layers of coherent QDs, for optoelectronic device applications such as infrared photodetectors. Our research has a strong experimental component which is usually complemented by theoretical analysis and modeling. We have already successfully modeled physical properties of materials, materials processes, and current transport in discrete devices and designed QHS to optimize device performance.  We will grow the semiconductor epilayers and nanostructures from the vapor phase in our own laboratory, and will characterize them ourselves or through a wide network of solid collaborations established through the years. We will use high-resolution X-ray diffraction, transmission electron microscopy, SQUID magnetometry and low temperature magneto-transport, and a combination of optical measurements such as optical absorption, photoluminescence (PL), PL excitation spectroscopy and time-resolved PL. Most of this research will build upon and extend our previous work in the area of strained III-V compounds (including dilute nitrides), with the addition of new organometallic precursors to grow Cr-, Gd- and Mn-containing alloys. Thus, additional funding is requested in a separate proposal to complete and upgrade a Metal Organic Vapor Phase Epitaxy reactor, dedicated to MS alloys. The objectives of our research are many-fold but the most relevant are:  (i) to enhance our understanding of the material properties (structural, optical, magnetic and transport) in relation to growth from the vapor phase and (ii) to design, improve and apply the QHS in innovative discrete device designs both for optoelectronic and spintronic applications. Novel magnetic semiconductor structures will open pathways to control and manipulate the spin of carriers which is expected to lead to novel information technologies.