Reversible optical properties (refractive index, n, and extinction coefficient, k) upon light soaking and annealing are predicted to originate from the metastable properties of hydrogenated amorphous silicon (a-Si:H). Optically programmable photonic devices can be demonstrated when a-Si:H is established as a potential programmable photonic material. Therefore, the effects of prolonged high intensity light soaking and annealing are investigated. A set of a-Si:H films is deposited by inductively coupled plasma-enhanced chemical vapor deposition (ICP-PECVD) near the amorphous/nano-crystalline phase transition that have significantly different hydrogen content and microstructures. Spectroscopic ellipsometry shows that the imaginary part of the pseudo dielectric function <ε2> values near the peak clearly decreases after light soaking and this decrease can be reversed after annealing. No loss of Si-bonded hydrogen is observed after repeated cycles of light soaking and annealing and an inverse correlation between this reversibility and the hydrogen content is found. A change in the bulk optical properties is likely the main contributor to the observed metastable effect, suggesting a reversible refractive index change. Repeated cycles of reversible <ε2> behavior are demonstrated which together with the magnitude of reversibility (as high as 3.7% at 3.6eV) illustrates the potential of a-Si:H for future programmable photonic devices.
|Number of pages||8|
|Journal||Physica Status Solidi A : Applications and material science|
|Publication status||Published - 20 Jun 2018|
- Hydrogenated amorphous silicon
- Pseudo dielectric function
- Refractive index
- Spectroscopic ellipsometry