Mn incorporation in as-grown and annealed (Ga,Mn)As layers studied by x-ray diffraction and standing-wave uorescence

TL;DR

This study uses advanced x-ray techniques to analyze how manganese atoms incorporate into (Ga,Mn)As layers during growth and annealing, revealing the roles of interstitial and substitutional Mn in lattice changes.

Contribution

It introduces a combined x-ray diffraction and standing-wave fluorescence method to distinguish Mn positions and their effects in (Ga,Mn)As layers during annealing.

Findings

Interstitial Mn causes lattice expansion and decreases with annealing.

Substitutional Mn remains stable during annealing.

Annealing reduces interstitial Mn concentration and lattice expansion.

Abstract

A combination of high-resolution x-ray diffraction and a new technique of x-ray standing wave uorescence at grazing incidence is employed to study the structure of (Ga,Mn)As diluted magnetic semiconductor and its changes during post-growth annealing steps. We find that the film is formed by a uniform, single crystallographic phase epilayer covered by a thin surface layer with enhanced Mn concentration due to Mn atoms at random non-crystallographic positions. In the epilayer, Mn incorporated at interstitial position has a dominant effect on lattice expansion as compared to substitutional Mn. The expansion coeffcient of interstitial Mn estimated from our data is consistent with theory predictions. The concentration of interstitial Mn and the corresponding lattice expansion of the epilayer are reduced by annealing, accompanied by an increase of the density of randomly distributed Mn atoms in the disordered surface layer. Substitutional Mn atoms remain stable during the low-temperature annealing.