The forbidden energy gap of a germanium semiconductor is 0.75 eV. The minimum thermal energy of electrons reaching the conduction band from the valence band should be -

Options

A. 0.5 eV
B. 0.75 eV
C. 0.25 eV
D. 1.5 eV

Answer

To determine the minimum thermal energy required for electrons to reach the conduction band from the valence band in a germanium semiconductor, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Energy Bands**: In semiconductors, there are two main energy bands: the valence band (Ev) and the conduction band (Ec). The energy gap between these two bands is known as the forbidden energy gap (Eg).

2. **Identify the Forbidden Energy Gap**: For germanium, the forbidden energy gap is given as 0.75 eV. This means that an electron in the valence band needs to gain at least 0.75 eV of energy to move to the conduction band.

3. **Determine Minimum Thermal Energy**: The minimum thermal energy required for an electron to transition from the valence band to the conduction band is equal to the forbidden energy gap. Therefore, the minimum thermal energy (Eth) needed is:
\[ Eth = Eg = 0.75 \, \text{eV} \]

4. **Conclusion**: Thus, the minimum thermal energy of electrons reaching the conduction band from the valence band in germanium is 0.75 eV.

### Final Answer:
The minimum thermal energy of electrons reaching the conduction band from the valence band should be **0.75 eV**.

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