Formation of high quality ohmic contacts to p-GaN using metal/transparent conducting oxides

Abstract

We report on promising NUtransparent conducting oxides for producing high quality ohmic contacts to p-GaN. It is shown that the contacts annealed at 450 -600 "C for 2 min in air ambient result in low specific contact resistances of lo-'lod ncm'. Based on the x-ray photoemission spectroscopy and Auger electron spectroscopy results, ohmic formation mechanisms are described.

Enhanced output of GaN-based light-emitting diodes with stripe-contact electrodes

“…Previously, it has been reported that the light transmittance of the Ni-Mg solid solution/Au contacts annealed at 550°C was better than 79% at a wavelength of 460 nm and the specific resistance was as low as ϳ10 −6 ⍀ cm 2 . 6 It was also reported that the light transmittance of the Ni/ Au contact annealed at 500°C was 88% at a wavelength of 470 nm, and the specific resistance was as low as 2.43ϫ 10 −2 ⍀ cm. 4 Others obtained low resistance Ni/ Au contact and increased the light extraction efficiency of nitride-based LEDs by intentionally roughening the p-GaN surface.…”

Assessment of Transparent Conducting Zinc Oxide as a Tunneling Contact to p-GaN

“…Achieving less resistive transparent ohmic contacts to p-GaN continues to be a challenge for fabrication of LED's given the large workfunction of p-GaN (due to its large bandgap of 3.4eV and electron affinity of 4.1eV) that varies depending on the amount of doping [3]. Achieving less resistive transparent ohmic contacts to p-GaN continues to be a challenge for fabrication of LED's given the large workfunction of p-GaN (due to its large bandgap of 3.4eV and electron affinity of 4.1eV) that varies depending on the amount of doping [3].…”

“…Several reports have been made earlier on the use of annealed Ni/Au ohmic contacts to p-GaN, but each have certain limitations for certain device architectures given the fact that the current crowds at the contact edges due to the highly resistive p-GaN [3]. The annealed Ni/Au contacts were only semitransparent in nature, the transparency being around 60-75% in visible and lower than 60% in UV region [4].…”