課程名稱︰ 數位電子學
課程性質︰ 必修
課程教師︰ 歐陽彥正
開課學院： 電資學院
開課系所︰ 資工系
考試日期（年月日）︰ 2008.04.10
考試時限（分鐘）：150 分鐘
是否需發放獎勵金：是
（如未明確表示，則不予發放）
試題 :
1.(15%)Given a silicon material doped with ND = 10^15 cm^(-3), the
resistivity of the semiconductor is given by σ=q(n*μn + p*μp)^(-1)
When the temperature of the semiconductor is raised, will its resistivity
increase or decrease based on the relation between the intrinsic carrier
density of a semiconductor and the temperature shown in Fig.1(Note that the
x-axis corresponds to reciprocal temperature) ? Please give your qualitative
explantion.
2.(15%)Following problem(1), if the increase of temperature is from 250K to
300K, will the change of resistivity negligible, i.e. less than 1% ?
3.(20%)A silicon material is doped with ND' = 10^19 cm^(-3) and ND'' = 10^14
cm^(-3) in different regions Fig2. Given that the diffusion and drift current
densities of electrons are equal to,
jp(diff) = (+q)*Dp*(-dp/dx) = -q*Dp*dp/dx A/cm^2
jn(diff) = (-q)*Dn*(-dn/dx) = +q*Dn*dn/dx A/cm^2
jn(drift) = Qn*Vn = (-qn)(-μn*E) = qnμnE A/cm^2
jp(drift) = Qp*Vp = (qn)(μn*E) = qpμpE A/cm^2
what is the voltage change across the semiconductor material ? Please specify
which side of the material, right or left, has a higher voltage.
4.(20%)Following problem(3), let the concentration of electrons at -x0 is 10^17
cm^(-3) and E(x) denote the magnitude of the electircal field at x. Given that
the magnitude of electrical field at x is equal to the amount of charge in the
region marked by the dot line divided by the permittivity of silicon, which is
denoted by ε, can you figure out a closed form of E(x) within -x0 and 0 in
terms of x0 and ε ?
5.(20%)Following problem(3), can you figure out which of the following 3
figures is the most accurate model of E(x) for x > 0 ? Please explain your
reasons.
6.(20%)Following problem(3), let xd denote the width of the depletion region in
x < 0. Can you write an equation about the concentration of electrons in x > 0
? The equation may contain integration and differentiation terms and you do not
need to obtain a closed form.
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※ 編輯: top90233a 來自: 220.137.202.120 (04/10 23:57)