| AVS 58th Annual International Symposium and Exhibition | |
| Energy Frontiers Focus Topic | Monday Sessions |
| Session EN+EM+NS-MoA |
| Session: | Nanostructured Materials for Third Generation Solar Cells |
| Presenter: | Shih-Hung Lin, Tohoku University, Japan |
| Authors: | S.-H. Lin, Tohoku University, Japan X.-Y. Wang, Tohoku University, Japan C.-H. Huang, Tohoku University, Japan Y. Ohno, Tohoku University, Japan M. Iagarashi, Tohoku University, Japan A. Murayama, Hokkaido University, Japan S. Samukawa, Tohoku University, Japan |
| Correspondent: | Click to Email |
Recently, 3-dimensional (3D) or 2-dimensional (2D) quantum dot superlattice are widely investigated to develop the new generation devices, such as quantum dot solar cell. Quantum dot superlattice consists of quantum dots with lower band gap energy in the matrix with higher band gap energy. For the device application, the structure requires high QD density, periodic QD array and uniform dot size and inter-dot spacing. Molecular beam epitaxy (MBE) and Metal-organic chemical vapor deposition (MOCVD) are two attractive methods among various bottom-up fabrication methods to fabricate quantum dots. However, there is limitation of bottom-up process to control the size, spacing and density of quantum dots. To brealkthrough these peoblems, we have proposed the ultimate top-down process by combination of bio-template and damage-free neutral beam etching (NBE) for fabricating defect-free 2D array of quantum dots.
In this study, we developed a series of novel process for fabricating uniform size and high density 2D array of GaAs nanodisk with unform inter-dot-spacing. Firstly, the hydrogen-radical treatment was used to remove the native oxide on GaAs surface. To utilize two-dimensional array of ferritin (protein including 7-nm-diameter iron core) as an etching mask, the formation of a hydrophilic 1-nm thick GaAs neutral beam oxidation film is key point. It is found that protein shell can be removed with oxygen-radical treatment at a low temperature of 280oC without thermal damage to GaAs. After protein shell removal, the iron oxide cores inside the ferritins remained on the surface. Then, using the iron core as an etching mask, neutral beam could etch the defect-free nanodisc structure of GaAs. Finally, we developed that iron oxide core was removed by wet etching with diluted hydrogen chloride and completed a fabrication process without inflicting any damage to GaAs. The result shows the quantum dot superlattice structure with a two-dimensional array of GaAs quantum dots with a diameter of ~7-nm, a height of ~10-nm, and a quantum dot density of more than 7×1011cm-2 was successfully demonstrated without any damage to GaAs.
This work is supported by the Core Research of Evolutional Science and Technology (CREST) of Japan Science and Technology Agency (JST).