Abstract
The thermal stability of the Cu/Cr/Ge/Pd/n+-GaAs contact structure was evaluated. In this structure, a thin 40 nm layer of chromium was deposited as a diffusion barrier to block copper diffusion into GaAs. After thermal annealing at 350°C, the specific contact resistance of the copper-based ohmic contact Cu/Cr/Ge/Pd was measured to be (5.1 ± 0.6) × 10−7 Ω cm2. Diffusion behaviors of these films at different annealing temperatures were characterized by metal sheet resistance, X-ray diffraction data, Auger electron spectroscopy, and transmission electron microscopy. The Cu/Cr/Ge/Pd contact structure was very stable after 350°C annealing. However, after 400°C annealing, the reaction of copper with the underlying layers started to occur and formed Cu3Ga, Cu3As, Cu9Ga4, and Ge3Cu phases due to interfacial instability and copper diffusion.
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Acknowledgement
The authors would like to acknowledge the assistance and support from the National Science Council, and the Ministry of Economic Affairs, Taiwan, R.O.C., under Contracts NSC96-2752-E-009-001-PAE, 95-EC-17-A-05-S1-020, and 96-EC-17-A-05-S1-020.
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Sahoo, K.C., Chang, CW., Wong, YY. et al. Novel Cu/Cr/Ge/Pd Ohmic Contacts on Highly Doped n-GaAs. J. Electron. Mater. 37, 901–904 (2008). https://doi.org/10.1007/s11664-008-0398-3
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DOI: https://doi.org/10.1007/s11664-008-0398-3