| AVS 62nd International Symposium & Exhibition | |
| Plasma Science and Technology | Friday Sessions |
| Session PS+SS+TF-FrM |
| Session: | Atomic Layer Etching (ALE) and Low-Damage Processes II |
| Presenter: | Yi-Chun Lai, National Chiao Tung University, Taiwan, Republic of China |
| Authors: | Y.-C. Lai, National Chiao Tung University, Taiwan, Republic of China A. Higo, Tohoku University, Japan C. Thomas, Tohoku University, Japan C.Y. Lee, Tohoku University, Japan T. Tanikawa, Tohoku University, Japan K. Shojiki, Tohoku University, Japan S. Kuboya, Tohoku University, Japan R. Katayama, Tohoku University, Japan T. Kiba, Hokkaido University, Japan I. Yamashita, Nara Institute of Science and Technology, Japan A. Murayama, Hokkaido University, Japan P.Yu. Yu, National Chiao Tung University, Taiwan, Republic of China S. Samukawa, Tohoku University |
| Correspondent: | Click to Email |
III-N quantum dots (QDs) gain media have generated great interest because of their desirable properties such as low threshold and temperature independence due to the discrete nature of the density of states. A uniform and high-density two-dimensional (2D) array of an isolated QD structure is required when considering applications in visible wavelength such as white LED. In general, size distribution, uniformity, and high-density are trade-offs when using a conventional self-assembly method; therefore, we have developed a technique that integrates a bio-template with neutral beam etching (NBE) process.
In this work, quantum nanodisks (QNDs) were fabricated from InGaN/GaN single quantum well (SQW) by using a bio-template and NBE. We developed a damage-less, top-down fabrication process for achieving high density of QNDs such as 2 x 1011 cm-2 embedded in 10 nm in diameter and 20 nm high nanopillars. The fabricated QNDs have great potential for fabricating quantum optoelectronic devices because of controllable diameter and thickness.
The InGaN/GaN SQW wafer was grown on a 2-inch c-plane sapphire substrate by metal-organic vapor phase epitaxy (MOVPE). The structure consisted of a 1μm-thick GaN buffer layer, 3nm-thick In0.1GaN and a 10nm-thick GaN capping layer. We used ferritins modified with polyethylene glycol (PEG ferritins) that include a metal oxide core for the etching mask. Oxygen annealing in vacuum was used to remove the ferritin protein shell at 350˚C, at chamber pressure of 32 Pa. Therefore the 7 nm diameter iron core was remained on the surface. Then hydrogen radial treatment, hydrogen passivation and NBE etching process were performed. At first, hydrogen radical treatment was realized to remove the surface oxide at chamber pressure of 32 Pa at 350˚C. Subsequently, hydrogen passivation was done to avoid any re-oxidation during the process. Finally, SQW was etched completely to form nanopillars using 40 sccm Cl2 at a chamber pressure of 0.1 Pa, with a substrate temperature of 100˚C, ICP power of 800 W and bottom electrode bias power of 10W. As a result, InGaN/GaN 10 nm in diameter and 20 nm high nanopillars could be fabricated. The etching profile was confirmed by Transmission electron microscopy (TEM).
After etching, we measured the photoluminescence (PL) and time-resolved PL (TRPL) to observe the quantum confinement energy levels. According to the PL measurements, we found an energy shift of 1.25 eV, from 2.9eV for SQWs to 2.75eV for QNDs. Although these measurements are still on-going now, we will clearly analyze and discuss the phenomena related to this shift in energy in the near future.