Physical modeling of high-speed PIN photodetectors

Crucial to accurate physical modeling of photodetector operation are the concepts of charge transport, both in depleted and undepleted absorption material, and charge collection, and their relationship to terminal current. This relationship is proven to involve both microscopic aspects of charge transport as well as macroscopic contributions which are well described by lumped circuit elements. The resultant model is applied to a generic PIN photodetector structure, and the relationship between impulse response, self-induced fields, two-dimensional illumination and a novel form of bandwidth collapse is discussed.