Highly enhanced Curie temperatures in low temperature annealed (Ga,Mn)As epilayers

TL;DR

This study demonstrates that low temperature annealing significantly increases the Curie temperature of (Ga,Mn)As epilayers, primarily due to enhanced hole density and surface effects, reaching up to 150 K.

Contribution

It reveals the impact of low temperature annealing and surface effects on increasing Curie temperatures in (Ga,Mn)As epilayers, a novel approach in ferromagnetic semiconductor research.

Findings

Curie temperature up to 150 K achieved

Enhanced free hole density correlates with higher T_C

Surface effects influence maximum T_C in epilayers

Abstract

We report Curie temperatures up to 150 K in annealed Ga1-xMnxAs epilayers grown with a relatively low As:Ga beam equivalent pressure ratio. A variety of measurements (magnetization, Hall effect, magnetic circular dichroism and Raman scattering) show that the higher ferromagnetic transition temperature results from an enhanced free hole density. The data also indicate that, in addition to the carrier concentration, the sample thickness limits the maximum attainable Curie temperature in this material - suggesting that the free surface of Ga1-xMnxAs epilayers is important in determining their physical properties.