Heteroepitaxial growth of highly anisotropic $Sb_{2}Se_{3}$ films on GaAs

TL;DR

This paper demonstrates the successful heteroepitaxial growth of anisotropic $Sb_{2}Se_{3}$ films on GaAs substrates, revealing significant optical birefringence and directional properties useful for advanced electronic and photonic devices.

Contribution

It introduces a novel method for epitaxial growth of anisotropic $Sb_{2}Se_{3}$ on GaAs, achieving controlled grain orientation and enhanced optical anisotropy at low and higher growth temperatures.

Findings

Achieved epitaxial $Sb_{2}Se_{3}$ grains on GaAs at 180-200°C.

Observed birefringence of 0.2 in-plane and >1 out-of-plane at telecom wavelengths.

Enhanced in-plane optical index anisotropy to 0.3 at higher growth temperatures.

Abstract

The epitaxial integration of anisotropic materials with mainstream cubic semiconductors opens new routes to advanced electronic and photonic devices with directional properties. In this work, we synthesize heteroepitaxial thin films of orthorhombic "quasi-1D" $Sb_{2}Se_{3}$ on cubic GaAs(001) using molecular beam epitaxy. Traditionally, the synthesis of anisotropic films with low symmetry materials is challenging due to multiple grain orientations that form. On a macroscopic scale, such a film tends towards isotropic properties, even if individual grains possess anisotropic responses. We achieve epitaxial $Sb_{2}Se_{3}$ grains on pristine homoepitaxial GaAs templates at low temperatures of 180-200 {\deg}C. With the $Sb_{2}Se_{3}$ 1D axis aligned in-plane to GaAs [110] and the primary van der Waals direction lying out-of-plane, we find a birefringence of 0.2 between in-plane orthogonal directions and a giant out-of-plane birefringence greater than 1 at telecom wavelengths. Growth at higher temperatures up to 265 {\deg}C yields $Sb_{2}Se_{3}$ of an unusual in-plane rotated texture that further enhances the in-plane optical index anisotropy to 0.3.