Transport and Magnetism in p-type cubic (Ga,Mn)N

TL;DR

This study investigates the electrical and magnetic properties of p-type cubic (Ga,Mn)N thin films, revealing high hole concentrations, shallow acceptor levels, and room temperature ferromagnetism, advancing understanding of magnetic semiconductors.

Contribution

It provides detailed characterization of p-type cubic (Ga,Mn)N, demonstrating high hole doping, shallow acceptor levels, and room temperature ferromagnetism, which are novel findings in this material system.

Findings

Hole concentrations >10^18 cm^-3 at room temperature

Presence of room temperature ferromagnetism

Shallow acceptor levels with ionisation energy 45-60 meV

Abstract

The electrical and magnetic properties of p-type cubic (Ga,Mn)N thin films grown by plasma-assisted molecular beam epitaxy are reported. Hole concentrations in excess of 1018 cm-3 at room temperature are observed. Activated behaviour is observed down to around 150K, characterised by an acceptor ionisation energy of around 45-60meV. The dependence of hole concentration and ionisation energy on Mn concentration indicates that the shallow acceptor level is not simply due to unintentional co-doping. Thermopower measurements on freestanding films, CV profilometry, and the dependence of conductivity on thickness and growth temperature, all show that the conduction is not due to diffusion into the substrate. We therefore associate the p-type conductivity with the presence of the Mn in the cubic GaN films. Magnetometry measurements indicate a small room temperature ferromagnetic phase, and a significantly larger magnetic coupling at low temperatures.