Register to reply

Finding Free Electrons and Hole Concentration

by l46kok
Tags: concentration, electrons, free, hole
Share this thread:
Sep8-07, 08:03 PM
P: 296
1. The problem statement, all variables and given/known data
Silicon is doped with an Aluminum Concentration of 2 X 10^16 cm^-3

What are the free electron and hole concentrations at room temperature?

What are the electron and hole mobilities at 300K?

What is the majority carrier? What is the minority carrier?

2. Relevant equations
n_0 * p_0 = (n_i)^2 [[(Concentration of Electrons) * ( Hole Concentration) = (Intrinsic Carrier Concentration)^2]]

n_i = 1.5 X 10^10 cm^-3 [[For Silicon]]

3. The attempt at a solution

This is actually for my electronics class, but this is more of a chemistry type question so I posted here.

I've missed few lectures and I'm already lost. Can anyone just start me off, provide me some hints and equations I should use to find the mobility?

As for the majority/minority carrier part, I understand that if the semiconductor is n-type, electrons are the majority carrier and holes are the minority carriers and the opposite for the p-type. How do you tell which type of material this is?
Phys.Org News Partner Science news on
'Office life' of bacteria may be their weak spot
Lunar explorers will walk at higher speeds than thought
Philips introduces BlueTouch, PulseRelief control for pain relief
Sep9-07, 06:27 AM
Astronuc's Avatar
P: 21,915
Please try not to miss class. Presumably one's textbook contains the necessary information.

For semiconductor like Si, if one adds trivalent atoms (Group 13 (IIIA) e.g. B, Al, Ga) to the Si lattice, the trivalent atoms will tend to accept loosely bound valence electrons from the Si atoms. This will produce a p-type semiconductor. Similarly, if adds pentavalent atoms (Group 15 (VA), e.g. N, P, As, Sb) to the Si lattice, the pentavalent atoms will donate an electron to the lattice, and this produces an n-type material.

See this -


Register to reply

Related Discussions
Concentration of conduction electrons Advanced Physics Homework 1
Stress Concentration around a circular hole on a flat rectangular plate General Engineering 5
Confused about Free Energy relation to Pressure & Concentration General Physics 1
Finding the concentration of a gas (thermodynamics) Biology, Chemistry & Other Homework 4