Unformatted text preview: EECE 254 Section 1 Quiz 2, Module II 1. What is your student number (please PRINT)? (5%) 2. What is your name (please PRINT)? (5%) 3. A pn‐diode has a built‐in voltage of 1.0 V, and a capacitance of X farads at a reverse bias of VR= 3 V. What reverse bias must be applied to reduce the capacitance to X/2 farads?(20%) 4. A silicon pn‐diode is formed with a very heavily doped p‐side of 1020 cm‐3, and n‐side for which the doping is much less (1016 cm‐3). Each side of the diode cross‐sectional area is 1 mm2. A forward bias of 0.75 V is applied to the diode. a. Compute the built‐in voltage of the junction.(10%) b. Compute the width of the depletion region at the stated forward bias.(10%) c. What fraction of the depletion‐region width appears on either side of the junction?(10%) 5. Given the diode equation, identify the contributions to this current of the flows across the depletion region due to: a. electron drift (5%) b. electron diffusion (5%) c. hole drift (5%) d. hole diffusion (5%) 6. Find the resistivity of (a) intrinsic silicon and (b) p‐type silicon with NΑ=1016/cm3. Use ni=1.5x1010/cm3, and assume that for intrinsic silicon μn=1350 cm2/V.s and μp=480 cm2/V.s and for the doped silicon μn=1110 cm2/V.s and μp=400 cm2/V.s. (20%) 7. Briefly explain how a MOSFET transistor operates (10%). Blank page. Use this page if you need more space to answer any of the questions. EECE 254 Section 2 Quiz 2, Module II 1. What is your student number (please PRINT)? (5%) 2. What is your name (please PRINT)? (5%) 3. A pn‐diode has a built‐in voltage of 1.0 V, and a depletion capacitance of X farads when in open‐circuit. What is the value of the depletion capacitance when a forward bias of 10 V is applied to the diode?(20%) 4. Consider a silicon pn‐junction diode doped with only acceptors on the p‐side to a concentration NA, and only donors on the n‐side to a concentration of ND. The equilibrium charge density distribution at 300 K on either side of the metallurgical junction (at x=0) is depicted below. x a. Indicate on the graphic above which side is n‐type and which side is p‐ type. Also, indicate which side is more heavily doped? Briefly state why you made the assignments you did. (10%) b. If ND=1017 cm‐3 on the n‐type side of the device, estimate the conductivity of the n‐type side of the device at 300 K.(10%) c. Which carrier dominates the reverse saturation current (holes or electrons)? Estimate the reverse saturation current for the diode assuming that all of this current is carried by the dominant carrier. Assume Ln=Lp=10 µm and the junction area is 104 µm2.(10%) 5. Consider a cube‐shaped sample of uniformly doped silicon at 300 K in which the equilibrium hole concentration is 1011 cm‐3. Metal electrodes cover two opposite sides of the sample. If the sample is heated or illuminated non‐ uniformly (close to one of the electrodes), and no voltage is applied, would you expect to observe a voltage difference between the two electrodes? Explain.(10%) 6. If, for a particular junction, the acceptor concentration is 1016 /cm3 and the donor concentration is 1015 /cm3, find the junction built‐in voltage. Assume ni= 1010/cm3. Also, find the width of the depletion region and its extent in each of the p and n regions when the junction is reverse biased with VR=5 V. At this value of reverse bias, calculate the magnitude of the charge stored on either side of the junction. Assume the junction area is 400 µm2. (30%) 7. Draw a schematic below showing the physical structure of a MOSFET transistor (10%). Blank page. Use this page if you need more space to answer any of the questions. ...
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- Spring '09
- Volt, 20%, 300 K, 30%, 1016 cm, 1011 cm, 2 farads