*Question E6E01:
Why is gallium arsenide (GaAs) useful for semiconductor devices operating at UHF and higher frequencies?*  

*Correct Answer is  B: Higher electron mobility*  

### AI Response: (may contain errors)  

Gallium arsenide (GaAs) is a semiconductor material that is particularly advantageous for high-frequency applications, such as UHF and above, due to its unique properties.

### Correct Answer: Higher electron mobility

- **Explanation**: 
  - GaAs has a higher electron mobility compared to silicon, which allows electrons to move more quickly through the material. This results in faster switching speeds and improved performance in high-frequency applications. Higher electron mobility is crucial for devices like transistors and amplifiers that operate at UHF and higher frequencies, as it enables them to handle higher frequencies with less signal degradation.

### Why the Other Choices are Incorrect:

- **A: Higher noise figures**: 
  - This is incorrect because GaAs typically has lower noise figures compared to silicon, making it more suitable for low-noise applications. A lower noise figure is desirable in high-frequency devices to maintain signal integrity.

- **C: Lower junction voltage drop**: 
  - GaAs does not have a lower junction voltage drop than silicon. In fact, GaAs devices often have a higher forward voltage drop. This characteristic is not advantageous for high-frequency operation.

- **D: Lower transconductance**: 
  - This is incorrect because GaAs devices can exhibit higher transconductance than silicon devices. Higher transconductance is beneficial for amplifying signals, especially at high frequencies.

### Summary

In summary, the key advantage of GaAs for UHF and higher frequency applications is its **higher electron mobility**, which allows for faster operation and better performance in high-frequency circuits. The other options do not provide the same benefits and are therefore not correct in this context.