Classify each of the following as being either a p-type or an n-type semiconductor
a. Ge doped with In
b. `B` doped with `Si`

Options

A. group 14 elements
B. group 15 elements
C. group 13 elements
D. group 18 elements

Answer

To classify the given semiconductors as either p-type or n-type, we need to understand the concepts of doping and the behavior of charge carriers in semiconductors.

### Step-by-Step Solution:

1. **Identify the Elements and Their Groups:**
- **Germanium (Ge)** is a group 14 element.
- **Indium (In)** is a group 13 element.
- **Boron (B)** is a group 13 element.
- **Silicon (Si)** is a group 14 element.

2. **Doping Germanium with Indium:**
- When germanium (a group 14 element) is doped with indium (a group 13 element), indium has one less valence electron compared to germanium.
- This creates "holes" (absence of electrons) in the crystal structure because indium cannot fully bond with the surrounding germanium atoms.
- The presence of these holes allows for conductivity through positive charge carriers.
- Therefore, **Ge doped with In is classified as a p-type semiconductor**.

3. **Doping Boron with Silicon:**
- When boron (a group 13 element) is doped with silicon (a group 14 element), silicon has one more valence electron compared to boron.
- This results in an excess of electrons in the crystal structure because silicon can donate an extra electron.
- The conductivity in this case is due to these extra electrons, which are negative charge carriers.
- Hence, **B doped with Si is classified as an n-type semiconductor**.

### Summary of Classification:
- a. **Ge doped with In**: p-type semiconductor
- b. **B doped with Si**: n-type semiconductor