课程名称︰光电导论 课程性质︰复选必修 课程教师︰吴育任 开课学院：电资学院 开课系所︰电机系 考试日期（年月日）︰2010/11/12 考试时限（分钟）：150+90 mins 是否需发放奖励金：是 谢谢 （如未明确表示，则不予发放） OpenBook 请在考卷上写下(中英皆可) "我以学生的荣誉发誓，这次考试我没有接受或是给予任何人帮助" 并签名，拒绝者考卷不会被批改及评分 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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