Quantum confinement in the conduction band of semiconductor heterostructures brings about fascinating optical properties in the infrared range of the spectrum due to intersubband transitions. Intersubband transitions refer to optical transitions between energy levels derived completely from a single conduction or valence band of the host material rather than optical transitions across the fundamental band-gap. Research on intersubband transitions in recent years has resulted in fundamental discoveries that eventually triggered practical device applications. In this talk I will focus on our efforts to creatively exploit the unique properties of nano-structured III-nitride materials for novel light emitters and detectors in the currently under-developed near- and far-infrared ranges. Due to large electron effective mass, the nitride intersubband materials require the ability to fine-tune the atomic structure at an unprecedented sub-nanometer level. I will describe our work to understand, model, and control the fundamental underpinnings of light generation and electrical transport in nitride nanostructures. Special attention will be given to the relationship between growth, structure, and optical properties in lattice-matched nitride heterostructures. We also report the first observation of exactly reproducible low-temperature negative differential resistance in c-plane nitride resonant tunneling diodes. These results lay the groundwork for future technological breakthroughs. Other research directions being pursued in our group will be briefly reviewed at the end of the talk.
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