Effect of SiO2 capping on the solid-phase-crystallized Ge thin films

Abstract

We investigated the impact of SiO2 capping layers with a thickness of 70 nm, deposited through plasma-enhanced chemical vapor deposition, on the crystalline quality and electrical properties of 300-nm-thick, solid-phase crystallized Ge thin films on SiO2/Si substrates. After the solid-phase crystallization at temperatures ranging from 425 to 500 °C, Ge thin films with SiO2 capping layers showed a faster crystallization rate, larger grains, and reduced energy barriers at grain boundaries compared to uncapped Ge films, resulting in enhanced carrier mobility. The Raman spectra and X-ray diffraction measurements suggested that the compressive stress in Ge thin films sandwiched with SiO2 layers is responsible for these enhancements. These findings demonstrate the substantial influence of SiO2 capping layers on the solid-phase-crystallized Ge thin films, which has far-reaching implications for the use of Ge-based materials in various technological applications.