# What happens when semiconductor melt?

• opuktun
In summary, a semiconductor melt is the process of heating a semiconductor material to its melting point, causing it to transition from a solid to a liquid state. As the material melts, its atoms become more mobile and the material exhibits properties such as lower density, higher electrical conductivity, and a higher diffusion coefficient. This melting process also affects the material's band structure, decreasing the band gap and potentially altering its electrical and optical properties. Semiconductor melts have various applications, including in the manufacturing of electronic devices and for crystal growth and research purposes.
opuktun

## Homework Statement

For intrinsic (undoped) silicon with a band gap of 1.1eV at 1500 K, what is the population of conduction electrons (m-3)? Comment on your result. Note that the melting point of silicon is 1687 K, and atom density of silicon is 5 x 10^28 atoms m-3.

Note: My main problem is to "comment"

## Homework Equations

http://hyperphysics.phy-astr.gsu.edu/HBASE/solids/fermi3.html#c1 <-- see here for the steps taken
In the end, I got 3.96x10^22 electrons/m3 which is close to the one given by the applet (maybe 'cos I used different values)

## The Attempt at a Solution

I was thinking of writing something like:
Although this equation may imply that increase in temperature will lead to increased conductivity (because increased no. of conducting electrons), we have to consider the state of the matter in which it is in. At higher temperature such as 1700 K, melting would have occurred. This may result in lower value of conductivity calculated than the actual. This is because melting would have caused the semiconductor to be in liquid state. Thus, the positive metal ions can carry charges along with the sea of electron.

But I'm not too sure if the bold sentence is correct. I would really appreciate it if you guys can give me some feedback on this answer.

Thanks!

Your calculation for the population of conduction electrons in intrinsic silicon at 1500 K is correct. The equation you used takes into account the band gap of silicon, which is an important factor in determining the number of conduction electrons. Your result of 3.96x10^22 electrons/m3 is also in close agreement with the value given by the applet, which suggests that your calculations are accurate.

However, it is important to note that this result is only valid for solid silicon at 1500 K. As you mentioned, at higher temperatures such as 1700 K, silicon would have melted and become a liquid. In this state, the positive metal ions can also carry charges along with the sea of electrons, which would affect the conductivity of the material. Therefore, the calculated value of conduction electrons may be lower than the actual value in a liquid state.

In conclusion, your calculation for the population of conduction electrons in intrinsic silicon at 1500 K is correct and your reasoning for the potential discrepancy at higher temperatures is valid. It is important to consider the state of the material when interpreting conductivity values.

Your response is on the right track. When a semiconductor melts, it transitions from a solid state to a liquid state. This transition can significantly affect the population of conduction electrons. In the case of intrinsic silicon at 1500 K, the calculated population of conduction electrons may be lower than the actual value due to the presence of positive metal ions that can also carry charges. This highlights the importance of considering the state of the material when analyzing its conductivity. Additionally, it is worth noting that the melting point of silicon (1687 K) is close to the temperature at which the calculation was performed (1500 K). This could also affect the accuracy of the calculated value.

## 1. What is a semiconductor melt?

A semiconductor melt refers to the process of heating a semiconductor material to its melting point, causing it to transition from a solid to a liquid state.

## 2. What happens to the atoms in a semiconductor melt?

As the semiconductor material melts, its atoms gain enough energy to break free from their fixed positions in the crystal lattice and move more freely, causing the material to become a liquid.

## 3. What are the properties of a semiconductor melt?

A semiconductor melt typically has a lower density and higher electrical conductivity compared to its solid state. It also has a higher diffusion coefficient, meaning that atoms can move more easily in the liquid state.

## 4. How does a semiconductor melt affect the material's band structure?

During the melting process, the band gap of a semiconductor material decreases due to the increased thermal energy of the atoms. This can affect its electrical and optical properties.

## 5. What are some applications of semiconductor melts?

Semiconductor melts are used in the manufacturing of integrated circuits, solar cells, and other electronic devices. They are also used in crystal growth processes and in the production of high-purity semiconductors for research and development purposes.

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