Temperature Dependence of the Band Gap and Exciton Photoreflectance in Layered Gallium Telluride

• DOI: 10.1021/acsami.4c17178
• Publication Date: 2025-02-03T22:39:46Z
• Authors: Carlo C. Sta. Maria; Po-Hung Wu; Denny Pratama Has...; Clara Sinta Saragih; Hien Giap; Duc Huy Nguyen; Yan-Ruei Chen; Giang Thi Phan; Duy Van Pham; Ji-Lin Shen; Chien-Chih Lai; Maw-Kuen Wu; Yuan-Ron Ma
• Keywords: Blueshift; Absorption edge; Telluride; Monoclinic crystal system; Gallium antimonide

Among Group III-A metal monochalcogenides, gallium telluride (GaTe) is one of the less studied materials in terms applications and optical characterization. For temperature dependence energy transitions GaTe, photoluminescence (PL) spectroscopy commonly used, photomodulated reflectance (PR) yet to be reported. In this work, layered monoclinic GaTe single crystals were synthesized by Bridgman technique used for investigation conduction band (CB) edge free-exciton (FX) state using PR spectroscopy. Both (i.e., absorption emission) present at room 1.656 1.647 eV CB transition (≡Eg) FX transition, respectively, show a blueshift cryogenic temperatures that can fitted with Varshni's equation. The estimated E(0) 1.794 Eg 1.776 0 K. ∼18 meV lower than gap (Eg) PL confirms emission only Eg. temperature-induced band-gap shifting related performing temperature-dependent photodetector experiments various incident light wavelengths. At 80 K, responsivity single-crystal energies wavelengths (735 845 nm) smaller relatively 630 nm light. This indicates low-temperature shift plays role optoelectronics.