The Theory of Giant Splash of Photoresponse in Semiconductors at Low-Level Illumination with Increasing Concentration of Deep Recombination Impurity

Recombination of excess (nonequilibrium) electrons and holes in semiconductors through impurity recombination centers (traps) known as trap-assisted (ShockleyRead-Hall) recombination is in many cases the dominant process. In this chapter, we develop the general theory of trap-assisted recombination and study in detail two key characteristics: (1) dependences of excess charge carriers’ lifetime and photoelectric gain on concentration N of recombination centers and (2) effectiveness of band-toband photoexcitation of charge carriers and photo-emf in semiconductors at low-level illumination considered outside quasi-neutrality approximation. We have done systematic mathematical and detailed physical analysis of considered characteristics. Giant splash of photoresponse in semiconductors with increasing re‐ combination center concentration N is caused mainly by the growth of charge carri‐ ers’ lifetime in orders of magnitude. Also, this factor is sufficient to provide an increase, in order of magnitude and more, in efficiency of charge carriers’ photoexcita‐ tion with increasing N. Results of strict analytical calculations (i.e., outside commonly used local approximation of quasi-neutrality) show, that, photoinduced local space charge affects substantially on giant splash of semiconductor photoelectric response with increasing concentration of recombination centers. The theory of giant splash of photoresponse in semiconductors at low-level illumination with increasing concentration of recombination centers could develop further through generalization of boundary conditions on semiconductor surfaces and current contact electrodes, accounting for nonuniformity of charge carriers’ photoexcitation along the line of current flow and fluctuation processes. The study of nonstationary (frequency domain and transient) characteristics is of particular interest. © 2015 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. It follows from physical essence of considered effects that similar effects can occur in other mediums with recombination of dissociative or ion-ion type, for example, in multicomponent plasma as well.