ZnO and MgZnO nanoparticles were prepared by the co-precipitation method utilizing zinc sulfate heptahydrate and magnesium sulfate heptahydrate; structural measurements were also carried out. An x-ray diffraction (XRD) study indicated that no peaks for other possible phases such as MgO or MgZn intermetallic compounds indicating pure wurtzite structure. All nanoparticles crystallized in a hexagonal wurtzite structure with different orientation diffraction peaks; the main peaks were (100), (002), and (101). Grain size (D) increased with increasing Mg concentrations. A scanning electron microscopy (SEM) analysis revealed that nanoparticle size increased by increasing the Mg concentration in a good qualitative with Scherrer equation and not only the size even the grain shape changed. In addition, optical measurements were taken infer that the band gap energy (Eg), extracted from Tauc’s plot, decreases with increasing of the Mg concentration doped, and found to be between 3.255 eV and 3.169 eV. The photoluminescence (PL) emission spectra show two peaks at the ultraviolet and green regions.

This work engineered the p-Electron Blocking Layer (p-EBL) of the AlGaN-based deep ultraviolet (UVC) light-emitting diode (LED) to achieve a high Radiative Recombination Rate (RRR). Carrier concentration can be efficiently injected into the active region by inserting an undoped thin AlGaN layer between the doped p-AlGaN layer as a superlattice. Compared with the UVC-LED with the bulk p-AlGaN EBL, the superlattice LED improves the optical power, holes and electrons concentration, and RRR.

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The demand for ultrahigh-speed, lightweight, low-cost, and defect-tolerant electronic devices drives the industry to switch to terahertz (THz) technologies. The use of two-dimensional (2D) materials has massively increased in THz applications due to their appealing electronic and optoelectronic properties, including tunable bandgap, high carrier mobility, wideband optical absorption, and relatively short carrier lifetime. Several 2D-material-based emitters, modulators, and detectors have been fabricated and examined. In this context, considerable research has been going on for 2D-material-based THz emitting sources, including materials and device structure to understand the electronics and optoelectronics mechanisms occurring in the THz region. This chapter focuses on the 2D-material-based emitters with insights into the background, the physical principle of photoconductive THz emitters, the 2D materials’ properties, and the research trends in the fabrication and characterization of the THz sources based upon 2D materials.