1
ECE 3150 Homework 2 Solution
Due 2/12/2009 by 11:10 AM
1.
(Poisson Equation and diffusion Length)
For a ptype extrinsic Si with the acceptor doping
N
A
=2
10
17
cm
3
, the minority mobility
n
=750cm
2
/Vs, the majority mobility
p
=300cm
2
/Vs, the
minority lifetime
n
=2
10
7
s, and the relative dielectric constant of Si is 11.7,
(a)
Estimate the potential curvature (defined from the Poisson equation) when the majority carriers
are somehow all depleted. (4 pts)
When the majority carrier is all depleted, the highest value for the net charge will be the
ionized doping concentration.
The potential curvature is then the net charged divided by
the dielectric constant:
qN
A
/
si
= 3.1
10
10
V/cm
2
.
(b)
If we start from a region where the net charge, electric field and electrostatic potential is all zero,
when we enter the majoritycarrier depleted region for 100nm, what are the values of the electric
field and electrostatic potential at the end of the 100nm charged region? (4 pts)
This preview has intentionally blurred sections. Sign up to view the full version.
View Full Document
This is the end of the preview.
Sign up
to
access the rest of the document.
 Spring '07
 SPENCER
 Semiconductors, Microelectronics, Electric charge, 100nm, diffusion length

Click to edit the document details