Name SAWANO Kentarou
Official Title Professor
Affiliation Electrical,Electronic and Communication Engineering
Profile ~Research~
My specialties are semiconductor engineering and crystal growth. Particularly my interests are silicon (Si)-related semiconductor materials, such as germanium (Ge) and SiGe alloys.

Today’s highly advanced electronics has been established by continual developments of the Si LSI based on miniaturization (scaling) of physical sizes of metal-oxide-semiconductor field-effect-transistors (MOSFETs), the most elementary devises in the LSI. However, serious problems have been imposed recently, such as the scaling limit and immense power consumptions due to very dense electric interconnections.
My research group is conducting several research subjects to overcome this problem imposed in the Si microelectronics field. One activity is the channel engineering of MOSFETs. By introducing new materials as alternatives to the Si channel, we aim to realize higher carrier mobilities in the channel, which can bring device performance improvements without the size scaling. To this end, we introduce germanium (Ge) as the channel material. An essential key technology we have is the crystal growth of high quality Ge thin films (5~20 nm thickness) on Si with molecular beam epitaxy (MBE) technique. This so-called Ge nano structure creates a quantum well which can confine carriers and enhance their mobility thanks to quantum effects. Moreover, our epitaxy technology enables the crystal strain engineering, which can further increase the mobility. Thus, these technologies to fabricate nano structures can highly boost electronic device performances.
Another research activity is development of Si-based photonic devices, such as light emitters, photo detectors, waveguides etc., on the Si platform toward realization of optoelectronic integrated circuits (OEIC), where electric circuits can be replaced by optical ones, leading to significant performance enhancements and reduction of power consumption. The most difficult and challenging technology is the creation of Si light emitters since the light emission from Si is naturally very poor. However, we have succeeded in the strong light emission by means of forming a high quality strained Ge on Si. The induced strain can modify the Ge band structure, resulting in enhancements of light emission efficiencies. We have been developing light emitting diode (LED) based on the strained Ge-on-Si, and very recently we have succeeded in obtaining very strong current-injected light-emission form the Ge-LED at room temperature, which is a promising result toward realization of on-chip optical interconnections.

I received the Ph.D. degrees in applied physics from the University of Tokyo, Japan, in 2005. The Ph.D. thesis concerned the development of high-quality strained Si/Ge heterostructures and their transport properties. In 2005, I joined Research Center for Silicon Nano-Science, Advanced Research Laboratories (ARL), Musashi Institute of Technology as an Assistant Professor. Since 2016, I have been a Professor at Department of Electrical Electronic Engineering in Tokyo City University (formerly M. I. Tech.). I have also been a group leader of Research Center for Nano-Electronics in ARL.
Research Field(Keyword & Summary)
  1. Strained Ge-on-Insulator

    We have developed Ge epitaxy and wafer transfer techniques that allow us to realize high quality strained Ge-on-Insulators on Si wafers.

  2. Strained Ge channel devices

    We have realized ultra high-mobility Ge channel MOSFETs.

  3. Ge Photonic devices

    We are researching strained-Ge and Ge quantum dot-based light emitters to realize highly efficient Si-based light emitting deveces and optical interconnections.

  4. Ge micro-devices

    We have fabricated highly strained Ge microbridges based on Ge-on-Si and GOI wafers. In the future, we aim to develop novel devices with new functions by combining micro-resonant structures with MEMS devices.

Representative Papers
  1. “Mobility Enhancement in Strained Si Modulation Doped Structures by Chemical Mechanical Polishing” K. Sawano, S. Koh, Y. Shiraki, Y. Hirose, T. Hattori, and K. Nakagawa Appl. Phys. Lett. 82, 412 (2003).
  2. “Fabrication of high-quality strain-relaxed thin SiGe layers on ion implanted Si substrates” K. Sawano, S. Koh, Y. Shiraki, Y. Ozawa, T. Hattori, J. Yamanaka, K. Suzuki, K. Arimoto, K. Nakagawa, and N. Usami Appl. Phys. Lett. 85, 2514-2516 (2004).
  3. “Compressive strain dependence of hole mobility in strained Ge channels” K. Sawano, Y. Abe, H. Satoh, Y. Shiraki, and K. Nakagawa Appl. Phys. Lett. 87, 192102 (2005).
  4. “Magnetotransport properties of Ge channels with extremely high compressive strain” K. Sawano, Y. Kunishi, Y. Shiraki, K. Toyama, T. Okamoto, N. Usami, and K. Nakagawa Appl. Phys. Lett. 89, 162103 (2006).
  5. “Strained-Si n-channel metal-oxide-semiconductor field-effect-transistors formed on very thin SiGe relaxed layer fabricated by ion implantation technique” K. Sawano, A. Fukumoto, Y. Hoshi, Y. Shiraki, J. Yamanaka, and K. Nakagawa Appl. Phys. Lett. 90, 202101 (2007).
  6. “Strain dependence of hole effective mass and scattering mechanism in strained Ge channel structures” K. Sawano, K. Toyama, R. Masutomi, T. Okamoto, N. Usami, K. Arimoto, K. Nakagawa, and Y. Shiraki Appl. Phys. Lett. 95, 122109 (2009).
  7. “Uniaxially strained SiGe(111) and SiGe(100) grown on selectively ion-implanted substrates” K. Sawano, Y. Hoshi, S. Kubo, S. Yamada, K. Nakagawa, Y. Shiraki Journal of Crystal Growth 401, 758–761 (2014). doi: 10.1016/j.jcrysgro.2014.02.014
  8. “Structural and electrical properties of Ge(111) films grown on Si(111) substrates and application to Ge(111)-on-Insulator” K. Sawano, Y. Hoshi, S. Kubo, K. Arimoto, J. Yamanaka, K. Nakagawa, K. Hamaya, M. Miyao, Y. Shiraki Thin Solid Films 613, 24-28 (2016). doi:10.1016/j.tsf.2015.11.020
  9. “Light emission enhancement from Ge quantum dots with phosphorous δ-doped neighboring confinement structures” K. Sawano, T. Nakama, K. Mizutani, N. Harada, X. Xu, T. Maruizumi Journal of Crystal Growth 477, 131–134 (2017) DOI: 10.1016/j.jcrysgro.2017.03.008
  10. “Strain engineering of Si/Ge heterostructures on Ge-on-Si platform” Kentarou Sawano, Youya Wagatsuma, Md. Mahfuz Alam, Kaisei Omata, Kenta Niikura, Shougo Shibata, Yusuke Hoshi, Michihiro Yamada and Kohei Hamaya ECS Transactions 98, 267-276 (2020). DOI: 10.1149/09805.0267ecst
Award 2009 JJAP (Japanese Journal of Applied Physics) Young Scientist Award
2010 Paper Award, The magnetics Society of Japan
2011 JSAP Silicon Technology Division Young Scientist Award
2018 JSAP Silicon Technology Division Paper Award
Grant-in-Aid for Scientific Research Support: Japan Society for Promotion of Science (JSPS)
Affiliated academic society (Membership type) JSAP
Education Field (Undergraduate level) Semiconductor devices, Optics engineering
Education Field (Graduate level) Nano electronics, Advanced devises