Low resistance and thermally stable Ti/Al-based Ohmic contacts to N-face n-GaN for vertical light-emitting diodes by using Ti(Ga) solid solution and TiN layers

• Published in: Journal of vacuum science & technology. B, Microelectronics and nanometer structures processing, measurement and phenomena Microelectronics and nanometer structures processing, measurement and phenomena, 2012-03, Vol.30 (2)
• Main Authors: Jeon, Joon-Woo, Yum, Woong-Sun, Seong, Tae-Yeon, Youl Lee, Sang, Song, June-O
• Format: Article
• Language: English
• ISSN: 1071-1023; 2166-2746; 1520-8567; 2166-2754
• DOI: 10.1116/1.3678490

The authors report on the formation of highly reliable Ti/Al-based ohmic contacts to N-face n-GaN for high-performance vertical light-emitting diodes by using Ti(Ga) solid solution and TiN layers. The Ti(Ga) solid solution layer is used to minimize the outdiffusion of Ga atoms from the n-GaN surface region. Unlike the Ti/Al contacts, the Ti(Ga)/Ti/Al and Ti(Ga)/TiN/Al samples exhibit ohmic behavior with contact resistivities of 3.9 – 4.8 × 10−4 Ωcm2 after annealing at 250 °C. It was further shown that unlike the Ti(Ga)/TiN/Al samples, the Ti/Al and the Ti(Ga)/Ti/Al samples are largely electrically degraded when annealed at 300 °C in an oven. Based on x-ray photoemission spectroscopy and secondary ion mass spectrometry results, ohmic formation and degradation mechanisms are briefly described and discussed.