High-temperature performance of ohmic contacts to n-type GaN and GaAs

Jehn-Huar Howard Chern; R. Jennifer Hwu; Laurence P. Sadwick

doi:10.1117/12.370168

12 November 1999 High-temperature performance of ohmic contacts to n-type GaN and GaAs

Jehn-Huar Howard Chern, R. Jennifer Hwu, Laurence P. Sadwick

Proceedings Volume 3795, Terahertz and Gigahertz Photonics; (1999) https://doi.org/10.1117/12.370168
Event: SPIE's International Symposium on Optical Science, Engineering, and Instrumentation, 1999, Denver, CO, United States

Abstract

Cu₃Ge was studied as an Ohmic contact to n-GaN and n- type GaAs. Specific contact resistance of Cu₃Ge to n- type GaAs was found to be sensitive to annealing conditions, doping concentrations, and Ge compositions. After vacuum annealing at 400 degree(s)C for 30 min, Cu₃Ge exhibited ohmic behavior to n-type GaN with doping concentrations of approximately 1.0 X 10¹⁸ cm^-3. Unprotected Cu₃Ge ohmic contacts suffered from oxidation when exposed at temperatures higher than 300 degree(s)C. Aging tests at 400 degree(s)C where Cu₃Ge covered with TiW and Au was used as ohmic contact to n-type GaAs, and TiPtAu covered with Au to p-type GaAs, revealed unchanged I-V characteristics after 120 hr annealing which showed that this contact was suitable for device application at high temperature. Pseudomorphic HEMT employing protected Cu₃Ge ohmic contacts and Ti/Pt/Au gates has achieved peak transconductance of 330 mS/mm at room temperature for 2- micrometers long gate. The I-V characteristic of Pd/Al, covered with TiW/Pt changed from Ohmic to Schottky after aging at 350 degree(s)C for 2 hours. By depositing a very thin Cr layer between Ti/Al and Au layers, contact resistance of Ti/Al contacts remained the same even after an aging of 130 hr at 350 degree(s)C and 130 hr at 400 degree(s)C. However, specific contact resistance increased from 2.4 X 10^-6 (Omega) cm² to 3.8 X 10^-6 (Omega) cm² after annealing at 500 degree(s)C for 2 hr.

Citation Download Citation

Jehn-Huar Howard Chern, R. Jennifer Hwu, and Laurence P. Sadwick "High-temperature performance of ohmic contacts to n-type GaN and GaAs", Proc. SPIE 3795, Terahertz and Gigahertz Photonics, (12 November 1999); https://doi.org/10.1117/12.370168

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