# Intrinsic Semiconductor

1. Nov 2, 2012

### Outrageous

In intrinsic semiconductor, electrons jump into conduction band, a hole is left in valence band.
My question is the above statement correct? I though the hole is something we imagine, how to say the hole is in the valence band?
If I said an electron is in valence band, is that implying that the energy level of that electron is lower compared to the electron in fermi level? Am I correct? or it has any other meaning?
Thank you.

2. Nov 3, 2012

### Ratch

Outrageous,

An intrinsic semiconductor means that the semiconductor is undoped. Holes and electrons in intrinsic semiconductor material are created in pairs when a semiconductor bond is broken. When an electron leaves the valance band, a hole is left behind. The hole and electron concentration will be equal and varies with the temperature of the intrinsic semiconductor.

In quantum mechanics (QM), a hole has a physical status as an electron does, including an effective mass, albeit a different effective mass than an electron.

The Fermi level in an intrinsic semiconductor is located close to the middle of the forbidden zone at room temperature. That means you will not find any free holes or electrons there, so the question is without meaning.

Ratch

3. Nov 4, 2012

### mzh

Remember that all is governed by quantum mechanics, meaning that the energy of the electrons is discrete. Initially, the electron populates a quantum mechanical state $k$ (eigenfunction of the Hamilton operator, also called orbital) and when it jumps to the conduction band (into another orbital it finds there) its original, ground-state orbital remains, it does not just vanish. In this sense, the hole is very real, its an empty orbital, however there is no observable for it (as the the wavefunction is also no observable, only the square modulus of the wavefunction).