ECE
Midterm_exam_07_solutions

# Midterm_exam_07_solutions - ECE 315 MIDTERM EXAM SOLUTIONS...

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ECE 315 MIDTERM EXAM SOLUTIONS Relative permittivity of Si=11.9, of SiO 2 =3.9 Permittivity of free space=8.85e- 14 F/cm Intrinsic carrier concentration 10 10 cm -3 Thermal voltage=.0259V 1. (10pts) Two regions of semiconductor material are doped with different concentrations of an n-type dopant. Region 1 has a value of 1x10 18 cm -3 while region 2 has a value of 1x10 16 cm -3 . The thickness of the material is .2x10 -4 cm. If 1 volt is applied as shown. The carrier mobility in both regions is u n =100cm 2 /V-s a. Calculate the current flowing in the circuit. Assume that current only flows in the doped regions b. What is the voltage drop across region 1 and region 2 c. Calculate the carrier velocity in region one and region2. Region 2 Region 1 1 V 2.5 um 5 microns 10 um 5 um sec / 10 9 . 9 10 10 99 . 100 100 sec / 10 2 10 5 01 . 100 100 59 . 1 1 99 . 01 . 10 24 . 6 10 25 . 10 5 10 10 / 100 10 10 602 . 1 1 24 . 6 10 25 . 10 5 . 2 10 5 / 100 10 10 602 . 1 1 , 4 4 2 2 3 4 1 1 2 1 2 1 2 2 2 5 4 4 4 2 3 16 19 2 4 4 4 2 3 18 19 1 1 cm E v cm E v E velocity A R R I VI V V V R R R V ohms Vs cm cm coul R ohms K Vs cm cm coul R qn A l R = = = = = = = = + = 2245 2245 + = = = = = = = - - - - - - - - - - - - - μ μ μ ρ ρ

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2. A Si MOS capacitor with a n + poly Si gate has an potential of φ s =.259 at the oxide-semiconductor interface and a bulk potential of -.42V a. Sketch the potential vs distance diagram, electric field vs distance diagram, charge vs distance diagram.
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