Low resistance ohmic contacts on wide band-gap GaN

• Published in: Applied physics letters 1994-02, Vol.64 (8), p.1003-1005
• Main Authors: Lin, M. E., Ma, Z., Huang, F. Y., Fan, Z. F., Allen, L. H., Morkoç, H.
• Format: Article
• Language: English
• ISSN: 0003-6951; 1077-3118
• DOI: 10.1063/1.111961

We report a new metallization process for achieving low resistance ohmic contacts to molecular beam epitaxy grown n-GaN (∼1017 cm−3) using an Al/Ti bilayer metallization scheme. Four different thin-film contact metallizations were compared during the investigation, including Au, Al, Ti/Au, and Ti/Al layers. The metals were first deposited via conventional electron-beam evaporation onto the GaN substrate, and then thermally annealed in a temperature range from 500 to 900 °C in a N2 ambient using rapid thermal annealing techniques. The lowest value for the specific contact resistivity of 8×10−6 Ω cm2, was obtained using Ti/Al metallization with anneals of 900 °C for 30 s. X-ray diffraction and Auger electron spectroscopy depth profile were employed to investigate the metallurgy of contact formation.