We report on current injection induced terahertz electroluminescence from 4H-SiC p-n junctions with operating temperature up to 270 K. The emission is assigned to intracenter optical transitions in donor centers, initiated by the injection of non-equilibrium carriers into the n-doped region of a SiC p-n junction. At a pumping current of 300 mA at 100 K, the integrated output power was 58 μW from the device surface with an area of 3 mm2. These results suggest that THz emitting devices can be fabricated with simple structures of SiC p-n junctions, with relatively high operating temperatures and reasonable output powers.

We report on injection induced terahertz electroluminescence from SiC p-n junctions. The emission is assigned to intracenter optical transitions in shallow donors, initiated by the injection.

Infrared semiconductor ring laser fabrication typically involves planarization of ridge waveguide device structures and deposition of metal electrodes for electrical pumping. Uniform planarization across large samples is difficult to achieve. This leads to inadequate electrical contact between portions of the ring resonator and the deposited metal electrode layer whereby the devices are not optimally pumped. This results in high threshold currents and device failure. The problem of inadequate electrical pumping on account of non-idea planarization has been addressed by utilizing a metallic etch mask instead of the commonly used photoresist 'soft' mask. The metallic mask remains intact after ridge etching and the other ensuing fabrication steps to form a continuous metallic cover above the entire device structure. This metallic cover ensures proper electrical contact between the ring resonator and the deposited metal electrode layer even when planarization imperfections render only certain portions of the resonator in proper electrical contact with the metal electrode layer. The proposed fabrication process has led to large diameter ring lasers with high yield and low threshold current levels. These devices are robust and exhibit stable operation over large current ranges in addition.

A fabrication process of three-dimensional Woodpile photonic crystals based on multilayer photolithography from commercially available photo resist SU8 have been demonstrated. A 6-layer, 2 mm x 2mm woodpile has been fabricated. Different factors that influence the spin thickness on multiple resist application have been studied. The fabrication method used removes, the problem of intermixing, and is more repeatable and robust than the multilayer fabrication techniques for three dimensional photonic crystal structures that have been previously reported. Each layer is developed before next layer photo resist spin, instead of developing the whole structure in the final step as used in multilayer process. The desired thickness for each layer is achieved by the calibration of spin speed and use of different photo resist compositions. Deep UV exposure confinement has been the defining parameter in this process. Layer uniformity for every layer is independent of the previous developed layers and depends on the photo resist planarizing capability, spin parameters and baking conditions. The intermixing problem, which results from the previous layers left uncrossed linked photo resist, is completely removed in this process as the previous layers are fully developed, avoiding any intermixing between the newly spun and previous layers. Also this process gives the freedom to redo every spin any number of times without affecting the previously made structure, which is not possible in other multilayer process where intermediate developing is not performed.

The study of point discharge current has been made using an isolated metallic sharp point raised above the earth's surface, A theoretical relation between the point discharge current, wind speed and the potential gradient has been derived and the results have been compared with experimental observations.