Temperature-dependent properties of Cu-doped ZnTe thin films deposited on SLG substrates via RF magnetron sputtering and E-beam techniques

Abstract

Copper doping in zinc telluride (ZnTe) thin films has been extensively studied for optoelectronic applications; however, challenges remain in optimizing temperature-dependent diffusion while minimizing defect-related emissions. Although numerous studies have explored Cu-doped ZnTe, comprehensive investigations using electron-beam (E-beam) evaporation remain limited, especially concerning its influence on diffusion dynamics, defect formation, and electrical properties. This study systematically examined Cu-doped ZnTe films fabricated via E-beam evaporation with a fixed 50 nm Cu layer deposited at three substrate temperatures (RT, 150 °C, and 300 °C), followed by rapid thermal annealing (RTA) at 100 °C and 200 °C for 1 h under a nitrogen atmosphere. An as-cast (non-annealed) sample was also analyzed as a baseline reference. By investigating the interplay between deposition and annealing temperatures, this work provided new insights into temperature-driven diffusion control mechanisms and their influence on the structural, morphological, and electrical properties of ZnTe: Cu films. The optimal sample (ZT-Cu_150_A200) exhibited a carrier concentration of 1.33 × 10²⁰ cm⁻³, a resistivity of 3.77 × 10⁻⁵ Ω cm, and a mobility of 1.68 × 10³ cm²/V·s, significantly improving electrical conductivity while minimizing defect-related losses. These findings establish a crucial correlation between thermal activation, Cu diffusion dynamics, and defect passivation, offering a refined approach for optimizing Cu-doped ZnTe thin films for enhanced electronic performance.