梁凯婵A(修改版).docVIP

CHAPTER 3 The semiconductor in Equilibrium Solution From Equation (3.43),we can write Or Comment As we have seen previously,the conerntretins of electrons and holdes can vary by orders of magnitude.The charge carrier that the greater concenteation is referred to as the majority carrier ,and the charge carrier that hae the lesser concerntion is referres to as the minority carrier.In this example, the electron is the majority carrier and the hole is the minority carrier. The fundamental seniconductor equation given by Equation(3.43) will prove to be extremely useful throughout the remainder of the text Exercise Problem EX3.6 Find the hole concentration in silicon at T=300K if the electron concentration is. Which carrier is the ,amjority carrier and which carrier is the minorituy carrier? (Ans.;hold,majority carrier;electron,minority carrier) 3.3.3 The Fermi=Dirac Intergral In the derivation of the Equations(3.11) and (3.19) for the thermal equilibrium electron and hole concentrations, we assumed that the Boltzmann approximation was valid.If the Boltzmann approximation does not hold, the thermal equilibrium electron concentration is written from Equation (3.3) as (3.44) If we again make a change of variable and let (3.45a) And also define (3.45b) indicates those sections that will aid in the total summation of understanding of seniconductor devices, but can be skipped the first time through the text. 3.3 Carrier Distributions in the Extrinsic Semiconductor Figure 3.10 The Fermi-Dirac integra F1/2 as a function of normalied Fermi energy. The we can rewrite Equation (3.44) as (3.46) The integral is defined as (3.47) This function.called the Fermi-Dirac integral,is a tabulated function of the variable (F.Figure 3.10 is a plot of the Fermi-Dirac integral.Note that if (F﹥0,then EF﹥EC;t