Article

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

ABSTRACT

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.

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    • "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]. "
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    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.
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