An investigation of a nonspiking Ohmic contact to n-GaAs using the Si/Pd system

• Published in: Journal of materials research Vol. 3; no. 5; pp. 922 - 930
• Main Authors: Wang, L. C., Zhang, B., Fang, F., Marshall, E. D., Lau, S. S., Sands, T., Kuech, T. F.
• Format: Journal Article
• Language: English
• Published: New York, USA Cambridge University Press 01-10-1988
• ISSN: 0884-2914; 2044-5326
• DOI: 10.1557/JMR.1988.0922

A low-resistance nonspiking Ohmic contact to n-GaAs is formed via solid-state reactions utilizing the Si/Pd/GaAs system. Samples with Si to Pd atomic ratios greater than 0.65 result in specific contact resistivity of the order of 10−6 Ω cm2, whereas samples with atomic ratios less than 0.65 yield higher specific contact resistivities or rectifying contacts. Rutherford backscattering spectrometry, cross-sectional transmission electron microscopy, and electron diffraction patterns show that a Pd, Si layer is in contact with GaAs with excess Si on the surface after the Ohmic formation annealing. This observation contrasts with that on a previously studied Ge/Pd/GaAs contact where Ohmic behavior is detected after transport of Ge through PdGe to the interface with GaAs. Comparing the Ge/Pd/GaAs system with the present Si/Pd/GaAs system suggests that a low barrier heterojunction between Ge and GaAs is not the primary reason for Ohmic contact behavior. Low-temperature measurements suggest that Ohmic behavior results from tunneling current transport mechanisms. A regrowth mechanism involving the formation of an n+ GaAs surface layer is proposed to explain the Ohmic contact formation.