Conventional light-emitting diodes (LEDs) always pursue the high brightness required for solid-state lighting. However, they always exhibit very low frequency bandwidth of tens MHz. In this letter, we investigate the fabrication and characterization of high-speed GaN-based blue LEDs. The frequency response of LEDs is mainly limited by its diffusion capacitance and resistance, and the injected carriers in the active region of the device. Through appropriate device design, galliumdoped Zinc oxide film deposited by atomic layer deposition is used as the top contact layer with high lateral resistance to self-confine the current injection. In addition, a smaller bonding pad is used to reduce the RC time constant. Thus, the GaN-based blue LEDs with a 75-µm diameter exhibit a 3-dB modulation bandwidth of 225.4 MHz and a light output power of 1.6 mW at the current of 35 mA. Such LEDs can be applied to visible light communication in future.

In this letter, we investigate the fabrication and characterization of high-speed GaAs-based near-infrared (near-IR) light-emitting diodes (LEDs) by using gallium-doped zinc oxide (GZO) as the current-spreading layer. For the GZO contacts to p + -type GaAs prepared by atomic layer deposition, the minimum specific contact resistance of 1.7 × 10 −5 -cm 2 is obtained. The GaAs-based near-IR LEDs with an aperture diameter of 59 μm and a smaller bonding pad of 80 μm have a low forward voltage of 1.7 V at 20 mA, a series resistance of 5.6 , the total capacitance of 17.5 pF, and a light output power of 4.6 mW at 50 mA. By the design of a ring-shaped electrode overlapping with GZO film, the LED exhibits a 3-dB modulation bandwidth of 107.8 MHz at a driving current of 50 mA owing to the increase of injected current density into the confined region.

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Inverted zinc oxide photonic crystal structures were fabricated from polystyrene sphere (PSS) template using the sol–gel solution of ZnO by spin-coating method. It is easily able to control and fabricate the photonic crystal structures using the self-organized PSS with a size of 193 nm. The inverted ZnO photonic crystal structures observed show the (111) tendency of the hexagonal compact arrangement formation. The resulting structures possess the photonic band gaps in the near-ultraviolet range and exhibit an enhanced photoluminescence spectrum. The technology can effectively increase the light output intensity or efficiency for the applications of optoelectronic devices.