Staircase 2 (IMAGE) University of Texas at Austin Caption Electrons multiply as they roll down the "staircase" as part of the avalanche photodiode. Credit The University of Texas at Austin. 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.