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Abstract: We report on the formation of low-resistance and transparent p-type ohmic contact for green GaN-based light-emitting diodes (LEDs) using Ni–Co solid solution(5 nm)/Au(5 nm) scheme. The as-deposited Ni–Co solid solution(5 nm)/Au(5 nm) contact shows nonlinear current–voltage () characteristics. However, annealing the sample at 550 ∘C in air results in the formation of ohmic contacts with specific contact resistance of 6.5×10−4 Ω cm2. The annealed sample shows light transmittance of 71.7% at a wavelength of 530 nm, which is better than that (64.9%) of oxidized Ni/Au contacts. Based on Auger electron spectroscopy and x-ray photoemission spectroscopy results, the annealing-induced improvement of the contacts is described and discussed. [Copyright &y& Elsevier]

Abstract: We report on the formation of reflective and low resistance Ag-based contacts to p-GaN using Ir interlayers for GaN-based near UV flip-chip light emitting diodes (FCLEDs). The as-deposited Ir/Ag contacts give non-linear current–voltage (I–V) behaviors. However, the contacts become ohmic with specific contact resistance of ∼10−4 Ωcm2 when annealed at temperatures 330–530°C for 1min in air. The 530°C-annealed Ir/Ag contacts give a reflectance of ∼75% at a wavelength of 405nm, which is somewhat higher than that (∼71%) of annealed single Ag contacts. It is also shown that the output power of the LEDs made with the annealed Ir/Ag contact is higher than that with the annealed single Ag contact. [Copyright &y& Elsevier]

Abstract: MgZnO(MZO) interlayers are introduced to form high-quality Ag-based ohmic contacts to p-type GaN (N a =4×1017 cm−3) for GaN-based flip-chip light-emitting diodes (LEDs). The MZO (2.5nm)/Ag (250nm) contacts become ohmic with specific contact resistance of 3.83×10−4 Ωcm2 and reflectance of ∼83% at a wavelength of 405nm when annealed at 530°C for 1min in air. It is shown that LEDs made with the MZO interlayers yield reverse leakage currents three orders of magnitude lower than that of LEDs without the interlayers. In addition, the LEDs fabricated with the MZO interlayers show higher output power as compared with the LEDs without the interlayers. [Copyright &y& Elsevier]

Abstract: We have investigated the annealing-induced improved electrical properties of In(10nm)/ITO(200nm) contacts with p-type GaN. The contacts become ohmic with a specific contact resistance of 2.75×10–3 Ωcm2 upon annealing at 650°C in air. X-ray photoemission spectroscopy (XPS) Ga 2p core levels obtained from the interface regions before and after annealing indicate a large band-bending of p-GaN, resulting in an increase in the Schottky barrier height. STEM/energy dispersive X-ray (EDX) profiling results exhibit the formation of interfacial In-Ga-Sn-oxide. Based on the STEM and XPS results, the ohmic formation mechanisms are described and discussed. It is also shown that patterning by nano-imprint lithography improves the light output power of blue LEDs by 18–28% as compared to that of LEDs fabricated with unpatterned In/ITO contacts. [Copyright &y& Elsevier]

Abstract: We report on the formation of low-resistance and highly transparent indium tin oxide (ITO) ohmic contacts to p-GaN using a Sn–Ag alloy interlayer. Although the as-deposited Sn–Ag(6nm)/ITO(200nm) contacts show non-ohmic behaviors, the scheme becomes ohmic with specific contact resistance of 4.72×10−4 Ωcm2 and produce transmittance of ∼91% at wavelength of 460nm when annealed at 530°C. Blue light-emitting diodes (LEDs) fabricated with the Sn–Ag/ITO contacts give forward-bias voltage of 3.31V at injection current of 20mA. LEDs with the Sn–Ag/ITO contacts show the improvement of the output power by 62% (at 20mA) compared with LEDs with Ni/Au contacts. [Copyright &y& Elsevier]