Improvement of the light output of AlGaInP-based light-emitting diode by employing highly transparent Au/ITO p-type electrode

We report on the development of highly transparent and low resistance Au/ITO ohmic contacts on a p-GaP window layer for AlGaInP-based light-emitting diodes (LEDs). When annealed at 400 °C, the Au/ITO (20/40 nm) contacts showed a specific contact resistance of 4.4 × 10⁻⁴ Ωcm², which is comparable to that of conventional AuBe/Au (130 nm/100 nm) contacts. At 617 nm, the AuBe/Au film was opaque, while the Au/ITO films had transmittances of 63.3–92.8%. The Au/ITO films exhibited low sheet resistances of 1.4–5.1 Ω/sq. LEDs fabricated with the Au/ITO electrodes gave forward voltages of 2.07–2.18 at 20 mA, which is comparable to that of the AuBe/Au contact (2.06 V). The LEDs with the Au/ITO electrode showed 9.8–46.1% higher light output power at 100 mA than that with the AuBe/Au electrode. On the basis of the X-ray photoemission spectroscopy (XPS) and scanning transmission electron microscopy (STEM) results, the annealing-induced electrical improvement is described and discussed.