Abstract
Enhanced absorption of especially long wavelength light is needed to enable the full potential of semiconductor nanowire (NW) arrays for optoelectronic applications. We show both experimentally and theoretically that a transparent dielectric shell (Al2O3 coating) can drastically improve the absorption of light in InAs NW arrays. With an appropriate thickness of the Al2O3 shell, we achieve four times stronger absorption in the NWs compared to uncoated NWs and twice as good absorption as when the dielectric completely fills the space between the NWs. We provide detailed theoretical analysis from a combination of full electrodynamic modeling and intuitive electrostatic approximations. This reveals how the incident light penetrates better into the absorbing NW core with increasing thickness of the dielectric shell until a resonant shell thickness is reached. We provide a simple description of how to reach this strongly absorbing resonance condition, making our results easy to apply for a broad wavelength range and a multifold of semiconductor and dielectric coating material combinations.
| Original language | English |
|---|---|
| Pages (from-to) | 863-874 |
| Number of pages | 12 |
| Journal | Nano Research |
| Volume | 5 |
| Issue number | 12 |
| DOIs | |
| Publication status | Published - 2012 |
| Externally published | Yes |
| MoE publication type | A1 Journal article-refereed |
Funding
We acknowledge George Rydnemalm, Mariusz Graczyk and Sören Jeppesen for assistance in sample processing and Professors Lars Samuelson, Heiner Linke, and Mats–Erik Pistol for stimulating discussions and support. This work was financially supported by the Swedish Research Council (VR), the Swedish Foundation for Strategic Research (SSF), the Nanometer Structure Consortium at Lund University (nmC@LU), European Union (EU) program Architectures, Materials, and One-dimensional Nanowires for Photovoltaics-Research and Applications (AMON-RA) (No. 214814), Nordic Innovation program NANORDSUN, Knut and Alice Wallenberg Foundation, E.ON AG as part of the E.ON International Research Initiative, the National Basic Research Program of the Ministry of Science and Technology of China (Nos. 2012CB932703 and 2012CB932700), and a Fellowship for Young International Scientists of Chinese Academy of Sciences (U. H.).
Keywords
- absorption
- core-shell
- InAs
- Nanowire array
- photovoltaics