The annealing mechanism of AuGe/Ni/Au ohmic contacts to a two-dimensional electron gas in GaAs/AlGaAs heterostructures

TL;DR

This study investigates the annealing process of AuGe/Ni/Au ohmic contacts on GaAs/AlGaAs heterostructures, identifying optimal parameters and mechanisms to improve contact quality for 2DEG devices.

Contribution

It provides a detailed model predicting optimal annealing conditions based on the 2DEG depth and annealing parameters, supported by microscopy and spectrometry analyses.

Findings

Optimal annealing temperature and time depend on 2DEG depth.

Identified the annealing mechanism through microscopy and spectrometry.

Proposed a predictive model for annealing parameters.

Abstract

Ohmic contacts to a two-dimensional electron gas (2DEG) in GaAs/AlGaAs heterostructures are often realized by annealing of AuGe/Ni/Au that is deposited on its surface. We studied how the quality of this type of ohmic contact depends on the annealing time and temperature, and how optimal parameters depend on the depth of the 2DEG below the surface. Combined with transmission electron microscopy and energy-dispersive X-ray spectrometry studies of the annealed contacts, our results allow for identifying the annealing mechanism and proposing a model that can predict optimal annealing parameters for a certain heterostructure.