Low Specific Contact Resistance of Gallium Zinc Oxide Prepared by Atomic Layer Deposition Contact on p⁺- GaAs for High-Speed Near-Infrared Light-Emitting Diode Applications

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 1.7×10-5Ω-cm2is 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 Ω, 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.