Question

The behavior of Ge as semi-conductor is due to width of: (A) Conduction band being large (B) Forbidden band being large (C) Conduction band being small (D) Forbidden band being small and narrow

Short answer

The behavior of germanium (Ge) as a semiconductor is due to the width of the forbidden band being small and narrow (option D). This allows electrons to easily transition from the valence band to the conduction band, enabling electrical conduction and the characteristic semi-conductive behavior.

Step-by-step solution

Understand the energy bands in semiconductors

In a semiconductor material like germanium, atoms are close together, and their energy levels combine to create energy bands. There are three main energy bands: 1. Valence band: The highest energy band with electrons involved in atomic bonding. 2. Conduction band: The energy band where free electrons can move through the material and participate in electrical conduction. 3. Forbidden band or bandgap: The energy gap between the valence and conduction bands where no electron states can exist.

Relate energy bands to the behavior of semiconductors

A material's conductivity heavily depends on the position of its valence and conduction bands. For a semiconductor, the forbidden band (or bandgap) is small enough that electrons can transition from the valence band to the conduction band due to thermal energy or other excitations. This allows the semiconductor to conduct electricity, and its conductivity increases with increasing temperature.

Identify the characteristic attribute of germanium

As a semiconductor, germanium has a relatively small forbidden band width, making it easier for electrons to transition to the conduction band, thereby allowing it to display its characteristic semi-conductive behavior.

Select the correct option

Based on our analysis, the behavior of germanium as a semiconductor is due to the width of the forbidden band being small and narrow. Therefore, the correct answer is: (D) Forbidden band being small and narrow