Stoichiometric growth of high Curie temperature heavily-alloyed GaMnAs

TL;DR

This study demonstrates the growth of heavily-alloyed GaMnAs films with high Curie temperatures using a combinatorial low-temperature molecular beam epitaxy technique, revealing that optimal stoichiometry yields consistent magnetic properties.

Contribution

It introduces a systematic growth method for heavily-alloyed GaMnAs with high Curie temperatures and challenges existing models by showing Curie temperature independence from Mn content.

Findings

Curie temperature of 150-165 K achieved.

High substitutional Mn content increases linearly.

Optimal properties found within specific stoichiometric conditions.

Abstract

Heavily-alloyed, 100 nm Ga1-xMnxAs (x>0.1) films are obtained via low temperature molecular beam epitaxy utilizing a combinatorial technique which allows systematic control of excess arsenic during growth. Reproducible, optimized electronic, magnetic and structural properties are found in a narrow range of stoichiometric growth conditions. The Curie temperature of stoichiometric material is 150-165 K and independent of x within a large window of growth conditions while substitutional Mn content increases linearly, contradicting the prediction of the Zener Model of hole-mediated ferromagnetism.