Projects per year
Abstract
The vast majority of Staebler-Wronski Effect(SWE) studies have been focused on understanding the
nature of metastable defects in hydrogenated amorphous silicon(a-Si:H), i.e. the optoelectrical
properties for photon energies below the bandgap. However, the effects of prolonged light
exposure and annealing on the optoelectrical properties above the bandgap have not been thoroughly
investigated. For photonic integrated circuits even refractive index changes as little as 1%, may have a
significant impact. Therefore, this work aims to study possible changes in the absorption properties
above the bandgap as enabled by high intensity visible light soaking and annealing. The parameter
used in this work to study such changes in absorption is the imaginary part of the pseudo dielectric
function <e2> derived by spectroscopic ellipsometric (SE) measurements. A set of a-Si:H films was
deposited near the amorphous/nanocrystalline phase transition at different substrate temperatures
having different microstructures by inductively coupled plasma enhanced chemical vapour
deposition(ICP-PECVD). For an a-Si:H film the <e2> value exhibits considerable change over time, as
the top surface undergoes oxidation during prolonged air exposure. Therefore, the light-induced and
annealing effects on these samples are investigated with respect to the corresponding twin samples
that are stored at room temperature in air to serve as a reference. The measured <e2> values around
the electronic polarization resonance clearly decrease after light soaking and can be completely
reversed after annealing (nearly 4%; see attached figures), indicating familiar metastable nature of
defects in hydrogenated amorphous silicon. Since no loss of bonded hydrogen is detected after
repeated light soaking and annealing cycles and considering the reversibility of the <e2> change, it is
believed that a change in the bulk optical properties is the main contributor to the observed metastable
effect suggesting reversible refractive index change. Optical simulations which take the sample surface
oxidation into account suggest that the effect may be explained through metastable volumetric
expansion.
Original language | English |
---|---|
Publication status | Published - 21 Aug 2017 |
Event | 27th International Conference on Amorphous and Nanocrystalline Semiconductors (ICANS 2017) - Seoul National university, Seoul, Korea, Republic of Duration: 21 Aug 2017 → 25 Aug 2017 Conference number: 27 http://tft.khu.ac.kr/icans2017/index.html |
Conference
Conference | 27th International Conference on Amorphous and Nanocrystalline Semiconductors (ICANS 2017) |
---|---|
Abbreviated title | ICANS (2017) |
Country | Korea, Republic of |
City | Seoul |
Period | 21/08/17 → 25/08/17 |
Internet address |
Keywords
- Hydrogenated amorphous silicon
- spectroscopic ellipsometry
- metastable optical properties
- refractive index
Fingerprint Dive into the research topics of 'Reversible above band gap absorption properties of Hydrogenated amorphous silicon (a-Si:H)'. Together they form a unique fingerprint.
Projects
- 1 Active
-
Zwaartekracht ECO Research Centre for Integrated Nanophotonics
Koonen, A. M. J. (., van Zantvoort, J. H. C., Smit, M., Cao, Z., van der Heide, S., Mamun, M., Shi, B., Perez, J. C., Mekonnen, K. A., Trinidad, A. M., Zhang, X. & Spiegelberg, M.
1/01/14 → 31/12/23
Project: Research direct