[試題] 99上 吳育任 光電導論

[gn02003330 ()]

課程名稱︰光電導論
課程性質︰複選必修
課程教師︰吳育任
開課學院：電資學院
開課系所︰電機系
考試日期（年月日）︰2010/11/12
考試時限（分鐘）：150+90 mins
是否需發放獎勵金：是  謝謝
（如未明確表示，則不予發放）

OpenBook

請在考卷上寫下(中英皆可)
"我以學生的榮譽發誓，這次考試我沒有接受或是給予任何人幫助"
並簽名，拒絕者考卷不會被批改及評分

1.
(a)What are the problems of the PN diode LED and why it is replaced by
double heterojunction LEDs?
(b)What are the advantages of the quantum well LED to double heterojuction LED
and what are the disadvantages?
(c)Why multiple quantum well LEDs are finally be used?

2.
A PN diode LED which Eg is 1eV, and Nc = 1*10^18 cm-3, Nv = 2*10^18 cm-3
Na = Nd = 5*10^17 cm-3, ε=10ε0 , μn = 1000cm2 V-1 sec-2
μp = 100cm2 V-1 sec-2, τe = τh = 10^-7 sec

(a)What is the depletion region width of the PN diode LED?
(b)For given τ, find the diffusion lengths and from the comparsion can you
guess it is a direct bandgap or not?

3.
What is group velocity? As mentioned in class, when we use SiO2 as the wave
propogation medium, why we like to the light operating at the wavelength of
1.33μm?

4.
The lattice constant versus bandgap is shown below
(a)If we want to use InGaN alloy (Inx Ga1-x N ) grown on GaN to make double
heterojunction LED to emit the light at the wavelength 500nm, what would be
In composition?
(b)If the light emitted from the LED can be considered as a point source, by
using lens whose focal length = 10cm, diameter = 10cm, we want to couple all
the light into the fiber, what is the shortest sd? In this case, what is the
sa? (Note that fiber core diameter is very small and also think about the
definition of NA)
Eg(GaN)=3.4eV  Eg(AlN) = 6.2eV  Eg(InN) = 0.7eV

5.
For organic light emitting diode to form a display, why the Active-Matrix OLED
(AMOLED) has better properties such as higher contrast ratio compared to
Passive-Matrix OLED(PMOLED)?
What are the meanings of LUMO and HOMO?

6.
For a dielectric film, the refraction is index n1, and the film thickness is
d. For light normally incident into film from air, what is the transmission
coefficient through the film? When transmission coefficient reaches maxima,
what is the relationship between wavelength and d? (Assume No absorption loss)

7.For an In0.5Ga0.5N single quantum well LED(GaN/In0.5Ga0.5N/GaN) to emit the
light at wavelength = 576nm , what is the suggested quantum well width?
me(GaN) = 0.2m0
mhh(GaN) = 0.6m0
me(InN) = 0.05m0
mhh(InN) = 0.4m0

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