Self-compensation in manganese-doped ferromagnetic semiconductors

TL;DR

This paper develops a theoretical model for interstitial manganese in Mn-doped ferromagnetic semiconductors, revealing how non-equilibrium growth conditions influence defect formation and magnetic properties.

Contribution

It introduces a density-functional theory-based explanation for interstitial Mn formation and its role in ferromagnetism in Mn-doped semiconductors.

Findings

Interstitial Mn forms easily near the surface during growth.

Each interstitial Mn compensates two substitutional Mn acceptors.

Maximum Curie temperature occurs at 0.5 holes per substitutional Mn.

Abstract

We present a theory of interstitial Mn in Mn-doped ferromagnetic semiconductors. Using density-functional theory, we show that under the non-equilibrium conditions of growth, interstitial Mn is easily formed near the surface by a simple low-energy adsorption pathway. In GaAs, isolated interstitial Mn is an electron donor, each compensating two substitutional Mn acceptors. Within an impurity-band model, partial compensation promotes ferromagnetic order below the metal-insulator transition, with the highest Curie temperature occurring for 0.5 holes per substitutional Mn.