私立中原大學八十八學年度研究所招生考試命題紙

所組別 : 電子工程學系甲組 科目 :半導體元件 考試時間 : 05月01日第3節


Total : 100 points

  1. The crystal structure of a compound semiconductor AB shown in Fig. 1 is composed of atoms A and B with atomic radii of 1.26 A°and 1.18 A° .(20%)
    2. (a)What is the name of this crystal structure?
    (b)What is the smallest interatomic distance?
    (c)What is the lattice constant?
    (d)How many atoms are in the primitive unit cell of this lattice?

  2. Consider the band diagram shown in Fig. 2. (12%)
    3. (a)How can one obtain such a band diagram?
    (b)Show in the figure the relevant energy levels for electrons in the quantum wells.
    Fig. 3 shows the relation between the lattice constants and the bandgaps of some semiconductors available.

  3. The Hall measurements at 77K on a p-type sample yielded the following values:

    4. current I=100μA, Hall voltage VH=10 mV, applied voltage V=10 mV. Fig. 4 shows a schematic view of the sample used. The sample length, width, and thickness are L=100μm, W=10μm and t=1μm, respectively. The magnetic field B=1000 Gs (0.1 Tesla). What is the carrier concentration and Hall mobility?(16%)

  4. The 1/C2 versus applied voltage relation in a silicon p+-n-n+ junction diode is measured to have a form shown in Fig. 5. Calculate the thickness of the n-region, the built-in voltage, and the Na and Nd concentrations in the p+ and n regions. The diode area is 10-3 cm2. Also calculate the width of the n-region. (20%)

  5. Sketch qualitative distributions of electrons in the base of an n-p-n BJT for
    6. (a)forward active mode
    (b)saturation mode
    (c)cutoff mode
    (d)reverse active mode. (12%)

  6. A diode with degenerate p-type and n-type regions can form a tunnel diode. The current-voltage (I-V) characteristic of the tunnel diode changes dramatically from that of a convention diode. (20%)
    1. What is a degenerate semiconductor?
    2. Draw the I-V characteristic curve of the tunnel diode and explain in short how does this result come out?
    3. A tunnel diode can be used as an oscillator when it is biased by a DC circuit to make the operating point enter which region of the I-V curve?

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