Performance of GaN-based light-emitting diodes fabricated using GaN epilayers grown on silicon substrates.

Light extraction of GaN-based light-emitting diodes grown on Si(111) substrate (GaN-on-Si based LEDs) is presented in this study. Three different designs of GaN-on-Si based LEDs with the lateral structure, lateral structure on mirror/Si(100) substrate, and vertical structure on mirror/Si(100) substrate were epitaxially grown by metalorganic chemical vapor deposition and fabricated using chemical lift-off and double-transfer techniques. Current-voltage, light output power, far-field radiation patterns, and electroluminescence characteristics of these three LEDs were discussed. At an injection current of 700 mA, the output powers of LEDs with the lateral structure on mirror/Si(100) substrate and vertical structure on mirror/Si(100) substrate were measured to be 155.07 and 261.07 mW, respectively. The output powers of these two LEDs had 70.63% and 187.26% enhancement compared to that of LED with the lateral structure, respectively. The result indicated this vertical structure LED was useful in improving the light extraction due to an enhancement in light scattering efficiency while the high-reflection mirror and diffuse surfaces were employed.

P-side up AlGaInP-based light emitting diodes with dot-patterned GaAs contact layers.

High-brightness p-side up AlGaInP-based red light emitting diodes (LEDs) with dot-patterned GaAs contact layer and surface rough structure are presented in this article. Initial LED structure of p-GaP/AlGaInP/GaAs is epitaxially grown using metal organic chemical vapor deposition technique. Using novel twice transferring process, the p-GaP layer is remained at the top side as both the current spreading and-window layer. Dot patterned GaAs contact dots are formed between main structure and rear mirror to improve light reflection and current spreading. Moreover, the surface of p-GaP window is further textured by nano-sphere lithography technique for improving the light extraction. Significant improvement in output power is found for AlGaInP LEDs with GaAs contact dots and roughened p-GaP window as compared with those of LEDs with traditional n-side up and p-side up structures without roughened surfaces.

Effects of crystallinity and point defects on optoelectronic applications of ß-Ga2O3 epilayers.

This study evaluates the effect of crystallinity and point defects on time-dependent photoresponsivity and the cathodoluminescence (CL) properties of ß-Ga2O3 epilayers. A synchrotron high-resolution X-ray technique was used to understand the crystalline structure of samples. Rutherford backscattering spectroscopy was used to determine the net chemical composition of the samples to examine the type and ratio of their possible point defects. The results show that in functional time-dependent photoresponsivity of photodetectors based on ß-Ga2O3 epilayers, point defects contribution overcomes the contribution of crystallinity. However, the crystalline structure affects the intensities and emission regions of CL spectra more than point defects.