The electrical conductivity of pure germanium can be increased by

Options

A. increrasing the temperature
B. doping acceptor impurities
C. doping donor impurities
D. irradiating ultraviolet light on it.

Answer

To solve the question regarding how to increase the electrical conductivity of pure germanium, we can analyze each of the provided options step by step.

### Step-by-Step Solution:

1. **Understanding Pure Germanium**:
- Pure germanium is a semiconductor that behaves as an insulator at absolute zero (0 Kelvin) because there are no free electrons available for conduction.

2. **Increasing Temperature**:
- When the temperature of germanium is increased, thermal energy is provided to the electrons. This energy allows some electrons to overcome the energy gap and move from the valence band to the conduction band, creating free electrons.
- **Conclusion**: Increasing the temperature increases the free electron concentration and thus increases electrical conductivity.

3. **Doping with Acceptor Impurity**:
- Acceptor impurities are typically trivalent (such as Boron). When these impurities are introduced into germanium, they create "holes" by accepting electrons from the germanium atoms.
- The presence of holes allows for the movement of charge, thus increasing the conductivity.
- **Conclusion**: Doping with acceptor impurities increases hole concentration, which enhances electrical conductivity.

4. **Doping with Donor Impurity**:
- Donor impurities are pentavalent (such as Phosphorus). When these impurities are added to germanium, they provide extra electrons (the fifth electron) that can move freely within the crystal lattice.
- This increases the concentration of free electrons, thereby increasing conductivity.
- **Conclusion**: Doping with donor impurities increases free electron concentration, which enhances electrical conductivity.

5. **Irradiating with Ultraviolet Light**:
- Ultraviolet (UV) light provides energy to the electrons in germanium, similar to increasing the temperature. This energy can excite electrons from the valence band to the conduction band, creating free electrons.
- **Conclusion**: Irradiating with UV light increases free electron concentration, thus increasing electrical conductivity.

### Final Conclusion:
All the given options (increasing temperature, doping with acceptor impurities, doping with donor impurities, and irradiating with ultraviolet light) can effectively increase the electrical conductivity of pure germanium.