Wavelength‐Dependent Anisotropic Optical Properties in Layered GaTe for Polarization‐Sensitive Applications

Abstract

Anisotropic layered GaTe has emerged as a potential material for polarization‐sensitive applications. The optical anisotropy in monoclinic GaTe is triggered by its in‐plane structural anisotropy, as each layer comprises periodic chain‐like structures along its b‐axis crystal direction. However, there is ambiguity in identifying the b‐axis in GaTe in existing reports. Proper identification is vital toward the fabrication of polarization‐sensitive photodetectors and light sources. Herein, this ambiguity is addressed and a systematic structural and polarization‐resolved optical study to identify the b‐axis in GaTe is reported for a multitude of different sample thicknesses and laser excitation wavelengths. The diffraction and Kikuchi line pattern results demonstrate the relevance of the structural anisotropy on the observed anisotropic photoluminescence (PL) in GaTe. The near‐infrared PL from GaTe (≈1.66 eV) exhibits a minimum (maximum) intensity when the laser excitation is polarized parallel (perpendicular) to the b‐axis. The PL peak position behavior as a function of increasing sample temperature (77–298 K) and laser power density is characteristic of radiative recombination of free/bound excitons. Furthermore, a broadband visible excitation window is identified for which GaTe exhibits PL anisotropy. These results highlight the potential of layered GaTe in polarization‐ and wavelength‐sensitive applications.

Keywords

• anisotropy
• GaTe
• near-infrared light emission
• polarization
• 2D materials