Structural Quality and Magnetotransport Properties of Epitaxial Layers of the (Ga,Mn)(Bi,As) Dilute Magnetic Semiconductor.

Tomasz Andrearczyk,Jerzy Wróbel,Anna Kaleta,Khrystyna Levchenko,Jaroslaw Z Domagala,Tadeusz Wosinski,Tadeusz Figielski,Piotr Dłużewski,Janusz Sadowski

doi:10.3390/ma13235507

Abstract

Structural analysis of epitaxial layers of the (Ga,Mn)(Bi,As) quaternary dilute magnetic semiconductor (DMS), together with investigations of their magnetotransport properties, has been thoroughly performed. The obtained results are compared with those for the reference (Ga,Mn)As layers, grown under similar conditions, with the aim to reveal an impact of Bi incorporation on the properties of this DMS material. Incorporation of Bi into GaAs strongly enhances the spin-orbit coupling strength in this semiconductor, and the same has been expected for the (Ga,Mn)(Bi,As) alloy. In turn, importantly for specific spintronic applications, strong spin-orbit coupling in ferromagnetic systems opens a possibility of directly controlling the direction of magnetization by the electric current. Our investigations, performed with high-resolution X-ray diffractometry and transmission electron microscopy, demonstrate that the (Ga,Mn)(Bi,As) layers of high structural quality and smooth interfaces can be grown by means of the low-temperature molecular-beam epitaxy method, despite a large difference between the sizes of Bi and As atoms. Depending on the applied buffer layer, the DMS layers can be grown under either compressive or tensile misfit strain, which influences their magnetic properties. It is shown that even small 1% Bi content in the layers strongly affects their magnetoelectric properties, such as the coercive field and anisotropic magnetoresistance.

Highlights

Dilute incorporation of bismuth atoms into a GaAs semiconductor strongly reduces its energy gap as well as the temperature dependence of the energy gap [1,2], which is especially useful in optoelectronic applications [3,4,5]
We present comparative results of structural analysis obtained by means of high-resolution X-ray diffractometry (HR-XRD) and transmission electron microscopy (TEM) for the epitaxial layers of both alloys grown under the compressive misfit strain as well as under the tensile one
We assume an appearance of a single magnetic domain inside such a small Hall bar at low temperatures, at least for the (Ga,Mn)As layers grown on GaAs substrate [21]

Summary

Introduction

Dilute incorporation of bismuth atoms into a GaAs semiconductor strongly reduces its energy gap as well as the temperature dependence of the energy gap [1,2], which is especially useful in optoelectronic applications [3,4,5]. Partial replacement of As atoms by much heavier Bi atoms, which causes a large relativistic correction to the GaAs band structure, strongly enhances the spin-orbit coupling strength in the Ga(Bi,As) ternary alloy [6,7]. The latter effect substantially affects electronic properties of semiconductors. We present comparative results of structural analysis obtained by means of high-resolution X-ray diffractometry (HR-XRD) and transmission electron microscopy (TEM) for the epitaxial layers of both alloys grown under the compressive misfit strain as well as under the tensile one. We report on the results of electrical transport measurements of those layers, which confirm substantial enhancement of the spin-orbit coupling strength in the layers as a result of Bi incorporation into the (Ga,Mn)As DMS

Materials and Methods

X-ray Diffraction Results

Transmission Electron Microscopy Results

Magnetotransport Properties

Conclusions