I'm studying semiconductors and i might need a little help with some questions: First the dynamic resistance is the internal resistance of the diodes , but it's called dynamic because it isn't constant, right? Does all semiconductors, pure and doped, have internal/dynamic resistance? The reason i claim this is because diodes and transistors have such a resistance and they are made of doped semiconductors. But some pure semiconductor devices like the photoresistor also have a resistance that changes with temperature or light. Is that internal resistance caused by the collision of the flowing electrons with the atoms of the semiconductive materials just like in ordinary resistors? If so, this explains why temperature and light can decreace it. In diodes and especialy the zener diodes is the internal resistance caused by the flowing electrons colliding with the semiconductor atoms, or by the depletion layer, or both? Thanks.