About cookies on this site Our websites require some cookies to function properly (required). In addition, other cookies may be used with your consent to analyze site usage, improve the user experience and for advertising. For more information, please review your options. By visiting our website, you agree to our processing of information as described in IBM’sprivacy statement. To provide a smooth navigation, your cookie preferences will be shared across the IBM web domains listed here.
Publication
Applied Physics Letters
Paper
Low-resistance nonalloyed ohmic contacts to Si-doped molecular beam epitaxial GaAs
Abstract
We have found evidence that the surface depletion charge density in molecular beam epitaxial n-GaAs doped heavily with Si approaches the Si concentration. In situ metallization of the as-grown surface of GaAs uniformly doped with Si at 1×1020 cm-3 yields a specific contact resistivity of 1.3 μΩ cm2, indicating a space-charge density about equal to the silicon density despite a measured bulk electron density of 4×1018 cm -3. This contact resistivity is among the lowest for nonalloyed ohmic contacts to n-GaAs. We attribute the large discrepancy between surface space-charge density and bulk electron density to the amphoteric behavior of silicon in GaAs. Surface Fermi-level pinning and arsenic stabilization create a surface depletion region where donor site selection predominates, whereas the extrinsic electron density in the bulk causes self-compensation.