Optimization of submicron Ni/Au/Ge contacts to an AlGaAs/GaAs two-dimensional electron gas

TL;DR

This paper presents a detailed study on fabricating and analyzing submicron Ni/Au/Ge contacts to a 2D electron gas in AlGaAs/GaAs heterostructures, emphasizing the impact of geometry, orientation, and germanium distribution on contact performance.

Contribution

It introduces optimized fabrication techniques for submicron Ni/Au/Ge contacts and elucidates the role of germanium distribution in achieving high transmission and low resistance contacts.

Findings

High-yield contacts with 0.5 μm area and resistance <400 Ω are achievable.

Contact performance is significantly affected by geometry and crystallographic orientation.

Germanium distribution within the contact is crucial for high transmission.

Abstract

We report on fabrication and performance of submicron Ni/Au/Ge contacts to a two-dimensional electron gas in an AlGaAs/GaAs heterostructure. Utilizing scanning transmission electron microscopy, energy dispersive x-ray spectroscopy, and low temperature electrical measurements we investigate the relationship between contact performance and the mechanical and chemical properties of the annealed metal stack. Contact geometry and crystallographic orientation significantly impact performance. Our results indicate that the spatial distribution of germanium in the annealed contact plays a central role in the creation of high transmission contacts. We characterize the transmission of our contacts at high magnetic fields in the quantum Hall regime. Our work establishes that contacts with area 0.5 square microns and resistance less than 400 Ohms can be fabricated with high yield.