Hi! I am having a bit of a problem comprehending the physics of the Haynes-Shockley experiment; specifically the one where the excess carriers are generated with a laser. In the ordinary experiment, some electrons or holes are physically injected through a contact, right? Thus, there will be more holes or electrons amongst the excess carriers, and when this pulse (which always moves like the minority carriers, right?) reaches the detector, a voltage change is registered. So far, so good. But now we use a laser for generating the carriers instead, kicking up electrons into the conduction band and therefore generating just as many excess holes as electrons! And since they all move like the minority carrier, they will pretty much stick together. So no pulse can be registered, since the positive and negative charges cancel out! This makes no sense; can anyone tell me where I am wrong? EDIT: Sorry, this probably belongs in the Electrical Engineering category. Could an admin please move it there?