Final Exam, ECE 448- Spring 2022, UIC Name:
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Final Exam, ECE 448 Transistors – Spring 2022
University of Illinois at Chicago
10:30 am to 12:30 pm on May 03, 2022
Name: UIN:
[30 points] PROBLEM # 1
Assume a hypothetical pn junction with the doping profile shown below, derive the
expression for the depletion width and the electric field under equilibrium conditions (Note
β€œa” is negative)
Final Exam, ECE 448- Spring 2022, UIC Name:
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[30 points] PROBLEM # 2
In a silicon MOS capacitor with an n-type substrate and a p + polysilicon gate (Ef = Ev),
the substrate doping is uniform with Nd = 2 Γ— 1018 cmβˆ’3. The oxide thickness is 3 nm. There
is a p + channel contact biased at -1V relative to the substrate. The voltage drop across the
oxide is Vox = βˆ’0.6 V.
(a) Determine the state of the channel region (accumulation, flat-band, depletion, strong
inversion, etc.).
(b) Determine the applied gate voltage.
(c) Sketch the charge density, electric field and energy band diagram for the system.
Final Exam, ECE 448- Spring 2022, UIC Name:
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[20 points] PROBLEM # 3
Calculate the base transit time in a npn transistor with NDE= 1019 cm-3
, NAB = 1017 cm-3
, VBE=
0.8V and a neutral basewidth W = 0.8 ΞΌm. Assume DnB= 18 cm2 s-1 and independent of position.
Final Exam, ECE 448- Spring 2022, UIC Name:
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[20 points] PROBLEM # 4
List the steps needed for fabricating an n-MOSFET device. Draw figures to illustrate your
response clearly.

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ECE 448 Final Exam, Spring 2022, UIC Name: Page 1 of 4
ECE 448 Transistors Final Exam – Spring 2022
Chicago’s University of Illinois
On May 3, 2022, from 10:30 a.m. to 12:30 p.m.
[30 points] Name: UIN: PROBLEM #1 Assume a hypothetical pn junction with the doping profile shown below, and calculate the depletion width and electric field under equilibrium conditions (Note: “a” is negative).
ECE 448 Final Exam, Spring 2022, UIC Name: Page 2 of 4 [30 points] PROBLEM # 2 The substrate doping in a silicon MOS capacitor with an n-type substrate and a p + polysilicon gate (Ef = Ev) is uniform, with Nd = 2 1018 cm3. The thickness of the oxide is 3 nm. A p + channel contact is biased at -1V.