ABSTRACT
This chapter elaborates the growth and device fabrication of III-N materials, which are considered to be ideal ultraviolet (UV) light-emitting diodes (LEDs) and have attracted considerable attention under the concept of saving energy and environment. A global treaty of the “Minamata Convention on Mercury” highlights the adverse effects of mercury on human health and environment. The import and export of certain mercury-based products will be forbidden by 2020. Therefore, UV-LEDs are considered a suitable alternative to conventional UV lamps. The UV region includes the wavelength ranges 315–400 nm for UVA, 280–315 nm for UVB, and 200–280 nm for UVC (or deep UV). The wavelength of near-UV is 300–400 nm and that of DUV is 200–300 nm. The UVA range has many applications, including UV curing (for coatings, inks, and resins), lithography, sensing (fluorescent labels), medical field (e.g., blood gas analysis), and security detection (ID cards and banknotes). The UVB range has applications in UV curing, lithography, medical application (e.g., for psoriasis), and sensing (e.g., of gases). The deep UV range applications include water and air purification, sterilization (food and medical equipment), and sensing (e.g., DNA and gases). In this chapter, we firstly introduce the background, theory, and source of these III-N materials. Then, the fabrication issues, including epitaxial growth, structure design, and device fabrication, are described. In manufacturing UV-LEDs, the wide-bandgap material aluminum nitride (AlN) and its alloy aluminum gallium nitride (AlxGa1 − xN) have been employed to prepare the multiquantum well structure. A metalorganic chemical vapor deposition system is used for fabricating UV-LED epitaxial wafers with the newly designed GaN and AlN templates for emitting wavelengths from near to deep UV. The improved epitaxial quality and corresponding optical performance are discussed in detail. Finally, the challenges and prospects for UV LEDs are emphasized.
