Semiconductor Device Physics for TFTs

Abstract

Two device physics topics are discussed in this chapter, namely, surface band bending and surface charges in the metal–insulator–semiconductor, MIS, structure, and electron-hole pair recombination/generation processes. The treat- ment of the MIS structure covers the relationship between the voltage on the metal gate, the induced surface charge in the semiconductor and the resulting surface potential. This is treated analytically, using single crystal equations, and the relationships are fundamental to the understanding of IGFET operation. Equally, the concepts are widely employed in analysing TFT behaviour. The electron-hole pair generation process underlies the leakage current behaviour of many semi- conductor devices, and can be applied to the analysis of TFT off-state behaviour. The recombination process determines steady state carrier concentrations under injection conditions, such as optical illumination. Finally, there is a brief discus- sion of carrier flow in semiconductor devices, including the equations used in numerical simulation packages.