Question

State whether each combination of elements would be expected to produce a semiconductor: (a) Ga and \(\mathrm{Sb},(\mathrm{b}) \mathrm{As}\) and \(\mathrm{N},(\mathrm{c}) \mathrm{B}\) and \(\mathrm{P}\) (d) \(\mathrm{Zn}\) and \(\mathrm{Sb}\), (e) \(\mathrm{Cd}\) and \(\mathrm{S}\).

Short answer

(a) Yes, (b) No, (c) Yes, (d) Maybe, (e) Yes.

Step-by-step solution

Understanding Semiconductors

First, recognize that semiconductors are typically composed of elements from groups III and V in the periodic table, or from adjacent groups such as II-VI.

Analyzing Ga and Sb

Gallium (Ga) is from group III, and antimony (Sb) is from group V. This combination forms a III-V semiconductor, similar to gallium arsenide (GaAs). Therefore, Ga and Sb are expected to form a semiconductor.

Analyzing As and N

Arsenic (As) and nitrogen (N) are both from group V. Combinations of elements from the same group do not typically form semiconductors, as semiconductors need a balance of free electrons (n-type) and electron-holes (p-type). Thus, As and N are not expected to form a semiconductor.

Analyzing B and P

Boron (B) is from group III, while phosphorus (P) is from group V. This combination can also form a III-V semiconductor, similar to materials like boron nitride or boron phosphorus compounds. Thus, B and P are expected to form a semiconductor.

Analyzing Zn and Sb

Zinc (Zn) is from group II, and antimony (Sb) is from group V. This can form a II-VI semiconductor, like zinc arsenide (ZnAs), even though Sb is from group V. Zn and Sb could form a semiconductor but are typically less common than other II-VI compounds.

Analyzing Cd and S

Cadmium (Cd) is from group II, and sulfur (S) is from group VI. This is a typical II-VI semiconductor combination, like cadmium sulfide (CdS). Therefore, Cd and S are expected to form a semiconductor.

Key concepts

Element Groups

The periodic table is divided into different columns known as groups. Elements in the same group have similar properties due to having the same number of valence electrons. These groups are crucial in determining the formation of semiconductors. For instance, elements from groups III and V in the periodic table often combine to form III-V semiconductors, while combinations of groups II and VI form II-VI semiconductors.
Understanding which group an element belongs to helps in predicting its chemical behavior and potential to form semiconductors. These groups are not only a guide for semiconductor formation but also relate directly to the element's ability to conduct electricity under certain conditions.

III-V Semiconductors

III-V semiconductors are composed of elements from group III and group V in the periodic table. Common examples include gallium arsenide (GaAs) and indium phosphide (InP). These materials are widely used in the electronics industry due to their ability to efficiently conduct electricity and their utility in optoelectronic devices.
The combination of group III elements, which have three valence electrons, with group V elements, which have five valence electrons, results in a perfect balance needed for semiconductor behavior. This property makes III-V semiconductors highly effective for applications like LEDs and high-frequency transistors.

II-VI Semiconductors

II-VI semiconductors are formed by combining elements from group II and group VI. These materials, such as cadmium sulfide (CdS) and zinc oxide (ZnO), are known for their optical properties and are used in lasers, photodetectors, and solar cells.
Similar to III-V semiconductors, the combination results in an ideal electronic structure that allows for electron movement, a requirement for semiconductors. These combinations are particularly useful in applications where wide bandgap materials are needed, allowing them to operate in high-temperature or high-power environments.

Periodic Table Groups

The periodic table organizes elements based on their atomic structure and properties. Groups, or columns, play a crucial role in identifying how elements might interact with each other. Each group has elements with the same number of electrons in their outer shell, which dictates their chemical properties.
For semiconductors, understanding these groups is essential. Elements from group III, like boron and gallium, have three valence electrons, while those from group V, such as nitrogen and phosphorus, have five. These cross-group interactions provide the foundation for forming compounds with semiconducting properties.

n-type and p-type Materials

Semiconductors need to be doped to enhance their conductivity, forming n-type or p-type materials.

• n-type: Created by adding group V elements to a semiconductor, increasing free electrons.
• p-type: Formed by adding group III elements, creating 'holes' or positive charge carriers.

This doping process allows the semiconductor to carry electrical current more efficiently. The balance between free electrons and holes allows for precise control of electrical conductivity, crucial for various electronic applications including transistors and diodes.