# Bandstructure and E-k diagrams

1. Mar 29, 2008

### Defennder

I'm currently taking a microelectronics course and I missed a couple of lectures due to illness. As a result, I didn't understand the lecture notes fully. I hope someone would be able to help me on this. I consulted the recommended textbook for this course but it turns out that it didn't cover this part of the course. The textbook is SO Kasap's Principles of Electronic Materials and Devices 3rd Edn

I tried searching the Internet but I got a lot of links to upper level solid state physics courses, which covered this in far too much detail which is not required for my course and served to confuse me even further. For example, my lecturer omitted the concept of reciprocal lattice vectors, and just about every web page I came across had that concept embedded somewhere. This is just so frustrating.

1. The problem statement, all variables and given/known data and attempted solutions

http://img237.imageshack.us/img237/6853/ekdiagramzv1.th.jpg [Broken]http://img153.imageshack.us/img153/9755/gebandstructurekl4.th.jpg [Broken]

1st picture:
What exactly do heavy, light and split-off bands refer to? What is split-off energy?
I did some searching on google and found out that heavy, light bands are also termed heavy-hole and light hole bands, which suggests that somehow holes are divided into heavy and light holes and they then reside in these appropriate bands.

As for what exactly heavy and light refers, to, I'm guessing that these are the effective masses given by $$\frac{{\hbar}^2}{\frac{d^2E}{dk^2}}$$ and that 'heavy' holes reside in the less curved valence band because $${\frac{d^2E}{dk^2}}$$ is smaller there compared to the light band, meaning that the effective mass of the hole in the heavy band is higher than that of the light band. Is this correct?

But I have no idea what is split-off band and split-off energy.

2nd picture:
The picture shows that the lowest energy state for the conduction band is at L point. My notes also show that Si's lowest energy state for valence band is at X point. In general does this mean that the reason why X,L points are important is because they coincide with the lowest energy level of the conduction band for indirect bandgap semiconductors? If so, why is this the case?

2. Relevant equations

Last edited by a moderator: May 3, 2017