Charge Transport in Semiconductors In a semiconductor under typical operating conditions, the electrical current is carried by which species?

Introduction / Context:
Semiconductor devices rely on two kinds of mobile charge carriers: electrons (negative charge) and holes (effective positive charge). Their relative contributions depend on doping, injection, illumination, and bias. Understanding that both carrier types can contribute simultaneously is fundamental to analyzing p–n junctions, BJTs, and CMOS circuits.

Given Data / Assumptions:

• Crystalline semiconductor (e.g., Si, Ge, GaAs).
• No extreme conditions like ionic conduction in electrolytes.
• Standard temperatures and fields where electronic transport prevails.

Concept / Approach:

In an intrinsic semiconductor, n = p and both species carry comparable current. In doped (extrinsic) material, majority carriers dominate, but minority carriers still contribute, especially across junctions and under forward bias where injection occurs. Thus, total current density J = q (n μn E + p μp E) + diffusion terms, showing additive electron and hole contributions.

Step-by-Step Solution:

Verification / Alternative check:

Hall-effect measurements and diode I–V characteristics require both carrier types to explain observed behavior (e.g., minority carrier storage, transistor action).

Why Other Options Are Wrong:

• “Only” electrons or holes ignores minority transport and intrinsic cases.
• Significant ionic conduction occurs in electrolytes/ionic solids, not standard semiconductors.

Common Pitfalls:

Assuming minority carriers are negligible in all situations; overlooking diffusion components in non-uniform doping or under gradients.

Final Answer:

Both holes and electrons