Abstract
Electrical engineering students were interviewed in order to reveal their understanding of important physics concepts needed for a semiconductor physics course. In particular, the concepts of diffusion, holes and doping were studied. We found that a hierarchy of understanding existed for all these concepts, where different students had grasped the concepts to different levels. Particular student conceptions are given. We think it is important for teachers in both the physics and the semiconductor physics courses to know about the existing student conceptions, in order to meet them in the education.