Photoluminescence study of hydrogen-passivated type-II silicon clathrate films
Phys. Rev. B 113, 115201 – Published 2 March, 2026
DOI: https://doi.org/10.1103/jt5j-gdyk
Abstract
While type-II silicon clathrates have shown promising room-temperature photoluminescence, their intrinsic optical properties remain unclear due to the presence of surface oxides, inhomogeneous and significant residual sodium concentrations, and contributions from disordered phases. These factors have hindered reliable identification of the emission band and limited development of the clathrates as light-emitting materials. In this work, we present a systematic photoluminescence (PL) study of deuterium-passivated, low-Na-doped, Si clathrate films, in which Na-related donor states and native defect levels are significantly reduced. A previously unrecognized emission feature associated with a surface oxide layer is identified and chemically removed, revealing a sharper emission spectrum composed of two dominant emission bands. We associate the higher energy band with the emission from the clathrate framework and the lower one with hydrogenated disordered or amorphous Si present as an impurity phase in the material. Temperature- and excitation-dependent PL measurements place the optical band gap of the clathrate phase near 1.9 eV, consistent with theoretical predictions. These results resolve long-standing ambiguities in Si clathrate PL emission and demonstrate a practical route to accessing near-intrinsic optical transitions. This lays the groundwork for engineering clathrate-based optoelectronic materials and highlights their potential as silicon-compatible light emitters.
