# Homework Help: Please Give me solutions for these questions:

1. Aug 25, 2008

### MSEN

1. Consider a piece of pure silicon 100 mm long with a cross sectional area of 1 mm2.
How much current would flow through this “resistor” at room temperature in response
to an applied voltage of 1 volt?

2. Estimate the resistivity of pure silicon in V cm at (a) room temperature, (b) 77K,
and (c) 1000°C.You may neglect the temperature dependence of the carrier mobility
in making this estimate.

3. a. Show that the minimum conductivity of a semiconductor sample occurs when
b. What is the expression for the minimum conductivity?
c. Is this value greatly different than the value calculated in problem 1.4 for the intrinsic
conductivity?

4. When a Au atom sits on a lattice site in a silicon crystal, it can act as either a donor
or an acceptor. ED and EA levels both exist for the Au and both are close to the middle of the silicon bandgap. If a small concentration of Au is placed in an N-type
silicon crystal, will the Au behave as a donor or an acceptor? Explain.

2. Aug 25, 2008

### MSEN

corrention for 3.a

a. Show that the minimum conductivity of a semiconductor sample occurs when n=ni*root(μp/μn)

3. Aug 25, 2008

### nicksauce

No one is going to give you the answers. They would be in violation of the rules and spirit of this website.

We can help you with your homework, but to do this you need to show an attempt at the solutions so that we know where you are having problems.

4. Aug 25, 2008

### MSEN

I am really sorry for that posting. I must try it by myself before posting the questions. I am again sorry. Hope to not do the same again.

5. Aug 25, 2008

### Astronuc

Staff Emeritus
MSEN, please write the respective equations for the each problem, then someone can point you in the right direction.

1. What is the relationship between voltage, V, current, I, and resistance R? The what is the relationship between resistance and resistivity, or reciprocally, conductivity?