Ohmic Contact Formation Between Metal and AlGaN/GaN Heterostructure via Graphene Insertion

TL;DR

This paper presents a novel, simple method using Cr/Graphene layers to form Ohmic contacts to AlGaN/GaN heterostructures, demonstrating temperature-independent carrier transport and potential for easier device fabrication.

Contribution

Introduces a graphene-based approach for creating reliable Ohmic contacts to AlGaN/GaN heterostructures, avoiding complex high-temperature processes.

Findings

Weak temperature dependence of contact suggests non-thermionic transport

Cr/Graphene acts like doped n-type semiconductor in contact

Method simplifies fabrication of AlGaN/GaN devices

Abstract

A simple method for the creation of Ohmic contact to 2-D electron gas (2DEG) in AlGaN/GaN high electron-mobility transistors (HEMTs) using Cr/Graphene layer is demonstrated. A weak temperature dependence of this Ohmic contact observed in the range 77 to 300 K precludes thermionic emission or trap-assisted hopping as possible carrier-transport mechanisms. It is suggested that the Cr/Graphene combination acts akin to a doped n-type semiconductor in contact with AlGaN/GaN heterostructure, and promotes carrier transport along percolating Al-lean paths through the AlGaN layer. This new use of graphene offers a simple and reliable method for making Ohmic contacts to AlGaN/GaN heterostructures, circumventing complex additional processing steps involving high temperatures. These results could have important implications for the fabrication and manufacturing of AlGaN/GaN-based microelectronic and optoelectronic devices/sensors of the future.