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SUVAM ROY
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Why is it opposite to that of an electron?
SUVAM ROY said:Why is it opposite to that of an electron?
Well I know what is effective mass, how it's expression is obtained, how it varies for electron with wavenumber 'k' (m* vs k graph). But can't understand why for hole the m* vs k graph is opposite to the graph of electron.ZapperZ said:Back up a bit. You haven't told us what you already know.
For instance, do you know how we obtain the 'effective mass' of anything in a solid? For example, the "electron" that is in a metal or semiconductor also has an effective mass. Do you know how that is obtained?
In the future, unless you want your question to drag on for people to figure out what exactly you are asking, you must put SOME effort in elaborating your question, but also what you already know and tried to find out. It is required in the PF Rules.
Zz.
SUVAM ROY said:Well I know what is effective mass, how it's expression is obtained, how it varies for electron with wavenumber 'k' (m* vs k graph). But can't understand why for hole the m* vs k graph is opposite to the graph of electron.
Thanks. It's just my conception was not that clear. Will you check if I am right or not.ZapperZ said:Then I don't understand why you have your problem.
For example, look at Page 1 of this link at the top figure of a generic band structure of a semiconductor:
http://users.physik.fu-berlin.de/~pascual/Vorlesung/WS05/Slides/WS05-06%20AdMat%20IT%20-%20L1b.PDF
The bottom of the conduction band (energy band 1), the second derivative of E vs k is positive, and thus, m* is positive. The top of the valence band (energy band 2) has a negative curvature, and thus, the second derivative is negative, giving a negative m*.
Thus, knowing how m* is derived, and knowing the band structure, you get what m* is. If you know these, why are you still having a problem in understanding it?
Zz.
The main difference between hole mass and electron mass is that electrons are negatively charged particles, while holes are positively charged particles in a semiconductor material.
The mass of an electron is measured in units of electron mass (me), while the mass of a hole is measured in units of effective mass (mh*). The effective mass is a measure of the particle's behavior in the material and is influenced by the crystal structure and other factors.
Hole mass is important in semiconductors because it affects the material's electrical and optical properties. In particular, the effective mass of holes determines their mobility, which is a measure of how easily they can move through the material under an electric field.
The effective mass of holes can impact the performance of electronic devices in several ways. For example, a higher hole effective mass can lead to lower carrier mobility and slower device operation. On the other hand, a lower hole effective mass can result in higher conductivity and better device performance.
While the mass of fundamental particles like electrons cannot be changed, the effective mass of holes can be influenced by the properties of the semiconductor material. By adjusting the material's composition and crystal structure, it is possible to modify the effective mass of holes and thus improve the performance of electronic devices.