CSE 112 – Electronic Devices and Circuits
Homework 1
Instructions
• Answer all questions below. Answers can be either typed on a computer or hand-written (including using a
tablet, for example). Final submission should be in the form of a PDF file through Canvas.
• Please write your homework in a well-organized and clear way. Make sure the steps are easy to follow, and keep
your solutions concise.
• Do not forget to include your full name and student ID
• Homework due date: Saturday, October 10, 2025 (11:59 pm PST)
• No late submissions will be accepted
CSE 112 – Electronic Devices and Circuits - Homework 1
2
Q1 (20%)
Calculate the value of ni for gallium arsenide (GaAs) at T = 300 K . The constant B = 3.56 × 1014 cm−3 K −3/2 and
the bandgap voltage Eg = 1.42 eV .
Q2 (20%)
For a silicon crystal doped with phosphorus, what must ND be if at T = 300 K the hole concentration drops below
the intrinsic level by a factor of 108 ?
Q3 (20%)
A n-type piece of silicon with a length of 0.1 µm and a cross-section area of 0.05 µm × 0.05 µm sustains a voltage
difference of 1 V . If the doping level is 1017 cm−3 , calculate the total current flowing through the device at T = 300 K .
(µn = 1350 cm2 /(V .s), µp = 480 cm2 /(V .s), q = 1.6 × 10−19 C)
Q4 (20%)
Figure 1 shows a p-type bar of silicon that is subjected to electron injection from the left and hole injection from
the right. Determine the total current flowing through the device if the cross-section area is equal to 1 µm × 1 µm.
(Dn = 34 cm2 /s, Dp = 12 cm2 /s, q = 1.6 × 10−19 C)
Figure 1: Carrier Injection
Q5 (20%)
Due to a manufacturing error, the p-side of a pn junction has not been doped. If ND = 3 × 1016 cm−3 , calculate the
junction built-in voltage at T = 300 K . (Hint: Since the p-side is undoped, it should be treated as intrinsic silicon.)
University of California, Irvine
Boris Vaisband (Fall 2025)