半导体物理学半导体 (9).pdf
ELECTRICAL CONDUCTION IN SOLIDSDrift Current02Electron Effective Mass03The Energy Band and the Bond Model 01 Concept of the Hole 04Metals,Insulators,and Semiconductors05The Energy Band and the Bond Model Two-dimensional representation of the covalent bonding in a semiconductor at T=0 K.The Energy Band and the Bond Model a)Two-dimensional representation of the breaking of a covalent bond.(b)Corresponding line representation of the energy band and the generation of a negative and positive charge with the breaking of a covalent bond.The E versus k diagram of the conduction and valence bands of a semiconductor at(a)T=0 K and(b)T0 K.The Energy Band and the Bond Model Drift CurrentdqNJNiiqJ1NiieJ1The asymmetric distribution of electrons in the E versus k diagram when an external force is applied.Electron Effective MassmaFFFexttotalintamFext*m*,called the effective massFor the case of a free electron,m is a constant For the electron near the bottom of the allowed energy band21)(kCEEcm*is a constant(a)The conduction band in reduced k space,and the parabolic approximation.(b)The valence band in reduced k space,and the parabolic approximation.Concept of the Hole)(fillediieJVisualization of the movement of a hole in a semiconductorThe electron near the top of the allowed energy band22)(kCEEv m*is a negative quantityConception：The particles at the top of the allowed energy band are the holes,with a positive charge.The hole,then,has a positive effective mass denoted by mp*(a)Valence band with conventional electron-filled states and empty states.(b)Concept of positive charges occupying the original empty states.Concept of the Hole Metals,Insulators,and SemiconductorsAllowed energy bands showing(a)an empty band,(b)a completely full band,and(c)the bandgap energy between the two allowed bands.Allowed energy bands showing(a)an almost empty band,(b)an almost full band,and(c)the bandgap energy between the two allowed bands.Metals,Insulators,and SemiconductorsMetals：Cu、Ag、Au Oxide:ReO3、IrO2、RuO2Metal Metal conductivityTwo possible energy bands of a metal showing:(a)a partially filled band and(b)overlapping allowed energy bands.
