Ultraviolet light-emitting diode arrays using Ga-doped ZnO as current spreading layer

In this article, the authors investigate the fabrication and characterization of the 4x4 GaN-based ultraviolet (UV) light-emitting diode (LED) array with a pixel size of 200x200 mu m(2) and a pitch of 200 mu m. For comparison, the single broad-area LED with a size of 400x400 mu m(2) is also fabricated from the same epitaxial wafer as a reference. The Ga-doped ZnO (GZO) film is used as a current spreading layer onto the ultraviolet LEDs to enhance the light output power. The GZO film with a thickness of 100nm was deposited by atomic layer deposition (ALD) and has an electron concentration of similar to 8x10(20)cm(-3), a low resistivity of similar to 4x10(-4)Omega cm, and a high transmittance of similar to 84% in the near UV wavelength range. The ALD-GZO film was also used as the internal wires to connect the pixels of an LED array. The LEDs have a peak wavelength of 370nm with a slight redshift at higher injection currents. The 4x4 LED array has a better performance in the maximum light output power density of 7.25W/cm(2) at 240mA and a highly linear light output power to injection current, while the broad-area LED only exhibits the maximum light output power density of 1.34W/cm(2) at 70mA. The single pixel of a 4x4 UV LED array reveals a maximum light output power density of 7.25W/cm(2) at 240mA and a wider divergence angle of 137 degrees, which are better than the broad-area LED of 1.34W/cm(2) at 70mA and 128 degrees, respectively. Finally, the authors show the demonstration of photos of an 8x8 LED array. Published under license by AVS.