| III-Nitride material system (AlGaInN) possesses wide tunable direct bandgap, large longitudinal optical phonon energy, inherit fast carrier dynamics; good carrier transport properties, high breakdown fields; and high robustness and chemical stability enabling for everyday to military and scientific applications such as illumination sources; bio-agent detection, concealed weapons/drugs detection; and space exploration.;The first spectrum of interest is the ultraviolet (UV) spectrum. Ultraviolet region is very important as many biological agents (such as smallpox and anthrax) are luminescent in UV. Scattering of short-wavelengths in atmosphere enables non-line-of-sight secure communications in rugged terrains whereas strong reflection/absorption of UV at ionosphere promises secure space-to-space communications. Where photomultiplier tubes are found to be bulky and fragile, and Si(C)-based photodiodes require external filter elements, compact high performance UV (Al)GaN avalanche photodiodes (APDs) can be employed.;The second spectrum of interest is the visible spectrum. The total annual energy consumption in the United States for lighting is approximately 800 Terawatt-hours and costs ;The third spectrum of interest is the terahertz spectrum. Terahertz spectral range offers promising applications for science (such as cancer detection), industry (such as product defect detection), and military (such as drug, concealed weapon or explosives detection), and III-Nitrides are the integral part of unique quantum cascade laser designs that are theoretically capable of THz lasing at room temperature.;In conclusion, this work demonstrates high performance (gains of 53000) in (AlGaN-based) ultraviolet detectors, conventional and novel (ZnO-InGaN) light emitting diodes in the visible spectra, intersubband devices covering near- to mid-infrared regime (1.0 to 5.3 microm), and GaN-based reliable and reproducible resonant tunneling diodes. My work shows that with proper device design and gap-engineering, the (sub)bands of AlGaInN can be engineered for a wide optical range from ultraviolet towards terahertz. |
