AlGaInP-Based LEDs With a ${\rm p}^{+}$ -GaP Window Layer and a Thermally Annealed ITO Contact

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.