Features of Creating Ohmic Contacts for GaAs/AlGaAs Heterostructures with a Two-Dimensional Electron Gas

Abstract

The literature concerning the features of creating ohmic contacts for GaAs/AlGaAs heterostructures with a two-dimensional (2D) electron gas with a high level of electron mobility is analyzed. The process of annealing the contacts based on the Ni/Au/Ge system is considered. The recommended published parameters of the layers to be sprayed and the regimes of their annealing are presented, which make it possible to obtain ohmic contacts with low resistance up to temperatures lower than 4 K. Several mechanisms are considered, which can lead to the experimentally observed dependence of the characteristics of the contact on its crystallographic orientation. A method for creating contacts using Au/Ge/Pd metallization, in which the contact is formed due to the mutual diffusion and interaction of metals and a semiconductor in the solid phase at temperatures lower than 200°C, is described. This ensures a higher degree of homogeneity of the contact in the composition and a smooth metal–semiconductor interface, and it can lead to decrease of the influence of orientation effects on the electric characteristics of the contact.