X. F. Zeng

AlGaInP-Based LEDs With AuBe-Diffused AZO/GaP Current Spreading Layer

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.

AlGaInP-Based LEDs With a

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.

{\rm p}^{+}

The authors report GaN-based light-emitting diodes (LEDs) with an Ag layer underneath an insulating SiO2 layer. It was found that we can not only achieve much better current spreading, but also prevent the light absorption by the opaque p-pad electrode. With 20-mA current injection, it was found that the output power of the LEDs with SiO2/Ag layers was 4.1% and 9.6% larger than those of the LEDs with a SiO2 layer and the LEDs without a SiO2 layer, respectively. It was also found that the 20-mA forward voltage only increased slightly, from 3.03 to 3.05 V, for the LEDs with the SiO2/Ag layers.

-GaP Window Layer and a Thermally Annealed ITO Contact

We reported the SiO2 nanopillars on microscale roughened surface on GaN-based LED to enhance light-extraction efficiency. ZnO nanoparticles were deposited on SiO2 as an etching mask before ICP etching SiO2 by successive ionic layer adsorption and reaction method (SILAR), and the different heights of SiO2 nanopillars on microroughened ITO/GaN were obtained after etching. Compared to a regular (flat surface) GaN-based LED, the light output power for a LED with microroughening was increased by 33%. Furthermore, the proposed LEDs with SiO2 nanopillars on microroughened surface show the enhancement in light output power by 42.7%-49.1% at 20 mA. The increase in light output power ismostly attributed to reduction in Fresnel reflection by rough surface. The height of SiO2 nanopillars was increasing cause resulting in more rough on the microscale surface of GaN-based LEDs.

GaN-Based LEDs With Omnidirectional Metal Underneath an Insulating

In this study, 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 x 10- 4 Ω cm 2 . Furthermore, the specific contact resistance could be improved to 1.57 x 10 -4 Ω cm 2 when the sample post-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 AlGaInP-based light-emitting diodes with a AuBe diffused metal layer.

{\rm SiO}_{2}

We successfully demonstrated that the Arplasmatreatment p-GaN surface increased the contact resistance of ITO/P-GaN serving as injection current deflection layer under the electrode pad. It was found that the Vf values of the two LEDs at 20mA were approximately 3.3V. Under a 20mA current injection, it was found that output powers of conventional LED and Ar-plasmatreatment LED on p-GaN surfaces were 9.8 and 11.08mW, respectively. We can increase the output power of GaN LEDs in 13% due to current blocking on the surface of p-GaN under the electrode pad by inserting the treatment with Ar plasma. It was also found that, after the reliability test for 72 hours the half lifetimes of conventional LEDs and LEDs with Ar-plasma treatment on p-GaN surface were about 49% and 55%, corresponding to the initial intensity, respectively.

Layer

UV GaN Schottky barrier photodetectors with a semi-insulating AlInN cap layer were proposed and fabricated. By inserting the AlInN cap layer, we can reduce the dark leakage current by more than 2 orders of magnitude compared with conventional devices. We can also use the AlInN cap layer to suppress the photoconductive gain, enhance the UV-to-visible rejection ratio, reduce the noise level, and enhance the detectivity.