Ultra-small InGaN green micro-light-emitting diodes fabricated by selective passivation of p-GaN.

Here, we proposed fabricating ultra-small InGaN-based micro-light-emitting diodes (µLEDs). The selective p-GaN areas were intentionally passivated using a H2 plasma treatment and served as the electrical isolation regions to prevent the current from injecting into the InGaN quantum wells below. Three kinds of green µLEDs, two squircle shapes with widths of 5 and 4 µm and one circular shape with a diameter of 2.7 µm, were successfully realized. The current-voltage characteristics indicate that the series resistance and the turn-on voltage increase as the dimension of the µLED decreases. This originates from the diffusion of the hydrogen atoms into the unexpected conductive p-GaN area. The light output power density and the calculated external quantum efficiency of the µLEDs from a 5-µm-squircle to a 2.7-µm-circle were enhanced by 10-20% when compared to 98×98µm2 µLEDs that were fabricated using mesa etching.

Optimal ITO transparent conductive layers for InGaN-based amber/red light-emitting diodes.

Fabrication of indium tin oxide (ITO) was optimized for InGaN-based amber/red light-emitting diodes (LEDs). A radiofrequency sputtering reduced the sheet resistivity of ITO at low pressures, and a subsequent two-step annealing resulted in a low sheet resistivity (below 2×10-4 Ωcm) and high transmittance (over 98%) in the amber and red regions between 590 nm to 780 nm. Double ITO layers by sputtering could form an excellent ohmic contact with p-GaN. Application of the double ITO layers on amber and red LEDs enhanced light output power by 15.6% and 13.0%, respectively, compared to those using ITO by e-beam evaporation.

Photoelectrochemical and crystalline properties of a GaN photoelectrode loaded with α-Fe2O3 as cocatalyst.

Nitrides are of particular interest in energy applications given their suitability to photocatalytically generate H2 from aqueous solutions. However, one of the drawbacks of nitrides is the decomposition they suffer when used in photoelectrochemical cells. Here, we report the improvement of the catalytic performance and chemical stability of a GaN electrode when it is decorated with Fe2O3 particles compared with an undecorated electrode. Our results show a higher reaction rate in the Fe2O3/GaN electrode, and that photocorrosion marks take more than 20 times longer to appear on it. We also characterized the crystalline properties of the Fe2O3 particles with transmission electron microscopy. The results show that the Fe2O3 particles keep an epitaxial relationship with GaN that follows the Fe2O3[Formula: see text]GaN[Formula: see text] and Fe2O3[Formula: see text]GaN[Formula: see text] symmetry constraints. We also characterized an Fe2O3 (thin film)/GaN electrode, however it did not present any catalytic improvement compared with a bare GaN electrode. The epitaxial relationship found between the Fe2O3 thin film and GaN exhibited the Fe2O3[Formula: see text]GaN[Formula: see text] and Fe2O3[Formula: see text]GaN[Formula: see text] symmetry constraints.