Fig.1 (IMAGE) Osaka University Caption Measurement system and observation image of TDs in GaN semiconductor by multiphoton excitation photoluminescence method. TDs are observed as dark lines. Credit Osaka University Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.