课程名称︰固态电子学
课程性质︰选修
课程教师︰吴育任 教授
开课学院：电资学院
开课系所︰电机系
考试日期（年月日）︰2014/06/18
考试时限（分钟）：180分钟
是否需发放奖励金：是
（如未明确表示，则不予发放）
试题 :
Open book, total 110 points but maximum one can get is 100
观念题 :
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)
计算题
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).