AlGaInP-based LEDs with a p+-GaP window layer and a thermally annealed ITO contact

Dept. of Electr. Eng., Nat. Cheng Kung Univ., Tainan, Taiwan
IEEE Journal of Quantum Electronics (Impact Factor: 1.89). 07/2011; 47(6):803 - 809. DOI: 10.1109/JQE.2011.2118744
Source: IEEE Xplore


In this paper, indium-tin-oxide (ITO) films were deposited on p-type GaP films with a AuBe-diffused metal layer to form ohmic contacts. Without the AuBe diffused into p-GaP films, the ITO deposited on p-GaP showed a non-ohmic characteristic. After the AuBe diffused, the ITO deposited on p-GaP displayed a linear current-voltage characteristic and the specific contact resistance showed 2.63 × 10-4 ω-cm2. Furthermore, the specific contact resistance could be improved to 1.57 × 10-4 ω-cm2 when the sample post-ITO-deposition annealed at 400°C. The transmittance of ITO film almost was kept at 90% in the wavelength range of 400-700 nm after thermal annealing. These results revealed that the ITO films can be a suitable transparent current spreading layer for the fabrication of AlGalnP-based light-emitting diodes with an AuBe-diffused metal layer. It was also found that the 20 mA forward voltages measured from LEDs with Device A, Device B, Device C and Device D were 1.97, 1.96, 1.95 and 2.66 V and the light output powers were 4.2, 5.7, 6.0 and 6.3 mW, respectively.

Download full-text


Available from: Shoou-Jinn Chang
  • Source
    • "In contrast, linear I-V relationship was observed from the sample with AuBe diffusion. This should be attributed to conversion of p − -GaP into p + -GaP by the AuBe diffusion process [16], [17]. Using the transmission line model (TLM) with pad spacing of 10 μm, it was found that specific contact resistance of AZO deposited on AuBe diffused p-GaP was 2.68 × 10 −4 -cm 2 [23]. "
    [Show abstract] [Hide abstract]
    ABSTRACT: We report the use of Al-doped ZnO (AZO) as the current spreading layer for AlGaInP-based light-emitting diodes (LEDs). It was found that AZO could form good ohmic contact with AuBe-diffused p-GaP. It was also found that the specific contact resistance could be further reduced from 2.68×10-4 to 1.52×10-4Ω-cm2 by performing rapid thermal annealing at 400 °C for 5 min in N2 ambient. Furthermore, it was found that output power of the LEDs with AZO current spreading layer was 6.2% larger than that of the LEDs with indium-tin-oxide current spreading layer. It was also found that LEDs with AZO current spreading layer also exhibit good electrical properties and good reliability.
    Full-text · Article · Oct 2013 · IEEE Journal of Quantum Electronics
  • [Show abstract] [Hide abstract]
    ABSTRACT: We have demonstrated that light output power of vertical AlGaInP-based light emitting diodes (LEDs) can be enhanced through use of a circular n(+)-GaAs/Ni/Ge/Au micro-contact array and an ITO current-spreading layer. We designed three different circular micro-contact arrays with different total areas and diameters for use as n-type electrodes in vertical AlGaInP LEDs. For comparison, LEDs with a normal linear-patterned n-type electrode were also fabricated. The results show that the circular micro-contact array for use an n-electrode in the vertical AlGaInP-based LEDs, greatly improved the uniformity of light output intensity, followed by increase in light output power. In addition, we also found that the total area of a circular micro-contact array and the thickness of the ITO current-spreading layer were important parameters for enhancing the light output power of the AlGaInP-based LEDs, due to a reduced light absorption in the circular micro-contact array and in the ITO layer. (C) 2013 The Japan Society of Applied Physics
    No preview · Article · Oct 2013 · Japanese Journal of Applied Physics
  • [Show abstract] [Hide abstract]
    ABSTRACT: A twice wafer-transfer technique can be used to fabricate high-brightness p-side-up thin-film AlGaInP-based light-emitting diodes (LEDs) with an indium-tin oxide (ITO) transparent conductive layer directly deposited on a GaP window layer, without using postannealing. The ITO layer can be used to improve light extraction, which enhances light output power. The p-side-up thin-film AlGaInP LED with an ITO layer exhibited excellent performance stability (e.g., emission wavelength and output power) as the injection current increased. This stability can be attributed to the following factors: 1) Refractive index matching, performed by introducing ITO between the epoxy and the GaP window layer enhances light extraction; and 2) The ITO layer is used as the current spreading layer to reduce the thermal accumulation in the epilayers.
    No preview · Article · Dec 2014 · Optics Express