Features of the Formation of Ni–GaAs Contacts Obtained by Electrolysis and Their Electrophysical Properties

Nickel contacts based on gallium arsenide are of interest from the point of view of their application in optoelectronics. The aim of this work is to study the contact structures of Ni–p-GaAs and Ni–n-GaAs. The object of study is the electrochemical contacts of nickel to crystalline gallium arsenide. The article presents studies of the topography of homogeneous electrochemical nickel films of nanometer thickness (50–100 nm) on the surface of a semiconductor. The current–voltage characteristics of metal–semiconductor contacts are experimentally obtained. The roughness of the GaAs substrate of the Ni film was studied using optical and probe microscopes. Nickel films were obtained using a Watts solution and a setup for the production of electrochemical structures by the drop method. To minimize the roughness of the nickel surface obtained by electrolysis, a mode of low current density is used. Using a theoretical model and experimental data, the contact resistances are calculated and their current–voltage characteristics are obtained. The parameters of nickel surface roughness, which affect the operational properties of contact structures, are determined. The features of the current flow through the electrochemically obtained Ni–GaAs contacts are revealed. It is shown that the resulting Ni–p-GaAs structures are Ohmic, and the current–voltage characteristics of the Ni–n-GaAs contacts have a nonlinear region at voltages less than 1.5 V. It is shown that the formation of an integral nickel film on the GaAs surface is possible when the Ni layer thickness exceeds the average substrate roughness.