Keiji Tanaka (born in December 1947 in Wakayama city) is a Japanese solid-state scientist.After receiving Master Degree in Hokkaido University in Sapporo in 1972, he worked as a member of Central Laboratory in Canon Inc. in Tokyo for two years. Then, he came back to the university as a research associate. He got Doctor Degree in 1980 with a thesis entitled “Photoinduced refractive-index changes in As-S amorphous semiconductor films”. He became a lecturer in Department of Applied Physics, associate professor, and full professor in 1991, retired in 2012, and is now Emeritus Professor. He got 1st Ovshinsky Award (2001), “Fellow” of Japan Society of Applied Physics (2010), and APEX/JJAP Editorial Contribution Award (2011).Koichi Shimakawa is a Fellow and Emeritus Professor of Gifu University, Japan. He is an internationally recognized researcher in the field of amorphous semiconductors. He was awarded OVSHINSKY AWARD 2003 for his contribution to the chalcogenide glasses. He has heldvisiting appointments at both Cambridge and Glasgow Universities, UK and was awarded the honorary visiting researcher’s position at Leicester University, UK.

• Introduction.- Structure.- Structural Properties.- Electronic Properties.- Photo-Electronic Properties.- Light-Induced Phenomena.- Applications.- Future Prospects.