Dependence of the electrical properties of Zn contacts to GaAs on the structural properties of the Zn-GaAs interface

Document Type

Article

Publication Date

1-1-1986

Abstract

Ohmic contacts to /7-type GaAs are extremely important in the fabrication of heterojunction lasers, integrat ed optical devices, and solar cells. The importance of the metallurgical properties of the Zn-GaAs interface in determining the contact resistance is described here. The contacts were formed by the deposition of several thousand angstroms of zinc onto p-type GaAs (Na- 4x 10i8cm’”3) substrates by evaporation in an ultrahigh vacuum system. The nonlinear current-voltage characteristics of as-deposited samples changed to linear characteristics after annealing the samples up to 300CC. The specific contact resistivities (pc) as determined by four-point probe were typically 2x 10~4fl cm2. Further annealing of the samples beyond 300 °C changed the linear current-voltage characteristics to nonlinear. The Auger depth profiles on samples which were as-deposited, annealed at 300eC and annealed up to 500 °C explain the variations in the electrical characteristics. If preferential Zn diffusion into GaAs at 300 °C caused the Ohmic behavior, further heating up to 500 °C resulted in ZnO formation degrading both the electrical and structural properties. © 1986, American Vacuum Society. All rights reserved.

Publication Title

Journal of Vacuum Science and Technology A: Vacuum, Surfaces and Films

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