課程名稱︰固態電子學
課程性質︰選修
課程教師︰吳育任 教授
開課學院：電資學院
開課系所︰電機系
考試日期（年月日）︰2014/06/18
考試時限（分鐘）：180分鐘
是否需發放獎勵金：是
（如未明確表示，則不予發放）
試題 :
Open book, total 110 points but maximum one can get is 100
觀念題 :
1. For a Si pn diode, if we want to form an ohmic contact on both p and n
sides with heavily doping method, "plot out" the complete pn diode
potential profile (Ec and Ev) including the detail potential shape near
the metal contact region ( both n and p contact). The metal W (tungsten)
is used for both sides. (10 points)
2. Please explain the C-V curve of a MOS capacitor shown in Fig. 10.29 for
both low frequency and high frequency. (9 points). If this is a n-type
MOS, what will CV looks like for both high and low frequency? (6 points)
3. For the space charge width problem and for a pn diode solar cell, if p-type
doping will create much larger defect centers for non-rediative recombi-
nation and the n-type doping region has less defect density no matter how
large doping we used. And we hope the depletion region has less defect
centers to avoid the nonradiative recombination. Shold we dope more in
p layer or the n layer? Why? Please plot out the expected pn diode
"potential profile" and explain. pn diode potential profile should be right
(7 points)
4. Please simply explain the pn junction breakdown mechanism at a large
reverse bias for Si where Na = Nd = 10^17 (cm^-3). (8 points)
5. If we want the smaller RC delay and use the diode as the capacitance,
should we make the diode operate at reverse bias range or forward bias
range? Larger bias or smaller? Why? (2 sentences to explain?) (5 points)
計算題
6. For a Si MOS structure, please calculate the maximum space charge width
for a doping concentration ("n-type") Nd = 5.0 x 10^16 (cm^-3). What will
happen if we contunue to increase the doping density? (10 points)
7. If we use Fig. 10.16 for a Au metal put on the p-Si where the doping
concentration is 10^16 (cm^-3). Follow the example of Ex. 10.3 and Ex. 10.4
in the textbook and the oxide thickness is 30nm with Q' = 10^11 (cm^-2).
ss
What is the flat band voltage, V ? And what is the threshold voltage
FB
V ? (20 points)
th
8. For a special semiconductor, we know all its parameters are exactly the
same as Si, the only difference is the bandgap, which is 2.0eV instead of
1.1eV.
(1) Please calculate the V of the pn diode make by this material.
bi
Na = Nd = 10^17 (cm^-3) at T = 300K (7 points)
(2) If the turn-on voltage for the Si pn diode with the same doping is
around 0.7V, what would be the turn-on voltage for this pn diode you
guess? (you don't need to calculate) (3 points)
9. For a "p-type" Si Schottky diode with Na = 10^16 (cm^-3), the metal is
using Cr (see table 9.1).
(1) Please plot out the potential band profile (Ec and Ev) of this p-type
Schottky diode.
(2) Assume the cross section area is 10^-4 (cm^-2). Please determine the
bias needed to induce 100uA (10 points) (similar to homework)
10.Please calculate the Si pn diode recombination current and diffusion
current density (A/cm^2) at Va = 0.65V, Na = Nd = 10^18 (cm^-3). The u =
n
1000 (cm^2/V-s) and u = 150 (cm^2/V-s). τ = τ = 10^-8 (s) (10 points)
p n p
Please plot out the pn diode current density, Jn, Jp, and Jtotal along
the device at this bias including diffusion current effect and recombi-
nation current effect (5 points).