The figure below shows the V-I characteristics of a semiconductor...

Based on the given $V-I$ characteristics graph:

1. The curves are plotted in the third quadrant, which means the device is operating under reverse bias (negative voltage and negative current).

2. The magnitude of the reverse current is in microamperes ($\mu$A) and it remains almost constant over a range of reverse voltages. This is known as the reverse saturation current.

3. The reverse saturation current increases as the intensity of incident light increases ($E_3 > E_2 > E_1$).

This behavior is characteristic of a photodiode. A photodiode is a semiconductor device that converts light into an electrical current. It is specifically designed to operate in reverse bias. When light falls on the photodiode, it generates electron-hole pairs, which increases the reverse current. This current is directly proportional to the intensity of the incident light.

Therefore, the device is a photodiode operated in reverse bias.

Answer: Photodiode operated in reverse bias