Physical Electronics
Dr. Maguu Muchuka
Electrical and Control Engineering Department
Faculty of Engineering and Technology
Egerton University
Dr. Maguu Muchuka Physical Electronics
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Drift Current in Semiconductors: Mechanisms and Calculations, Lecture notes of Engineering
This document delves into the mechanisms of current flow in semiconductors, focusing specifically on drift current. it explains drift current as the movement of charge carriers (electrons and holes) due to an applied electric field. A detailed explanation of how to calculate drift current density, considering both electron and hole contributions. it also includes examples for intrinsic and extrinsic semiconductors (n-type and p-type), illustrating the calculations with a solved example for silicon. The educational value lies in its clear explanation of fundamental semiconductor physics concepts and their practical application.
Typology: Lecture notes
2024/2025
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Physical Electronics
Dr. Maguu Muchuka
Electrical and Control Engineering Department Faculty of Engineering and Technology Egerton University
Current flow in Semiconductors
The Mechanisms for movement of charge carriers
Current flow in Semiconductors
The Mechanisms for movement of charge carriers (^1) Drift The movement of charge carriers caused by electric field Results to drift current (^2) Diffusion The movement of charge carriers caused by variation in the carrier concentration Results to diffusion current
V
E
+ -
V
E + -
The figure shows a piece of semiconductor material
Let E be the applied electric field
V
E + -
The figure shows a piece of semiconductor material
Let E be the applied electric field
The field will produce a force that will act on free electrons and holes
V
E + -
The figure shows a piece of semiconductor material
Let E be the applied electric field
The field will produce a force that will act on free electrons and holes
The holes will accelerate in the direction of E as shown by the arrow
The electrons are accelerated in the opposite direction to that of E as shown by the arrow
The free electrons acquires a drift velocity Vn−drift
The free electrons acquires a drift velocity Vn−drift
Vn−drift = −μnE μn is the electron mobility
The free electrons acquires a drift velocity Vn−drift
Vn−drift = −μnE μn is the electron mobility
The holes acquires a drift velocity Vp−drift
The free electrons acquires a drift velocity Vn−drift
Vn−drift = −μnE μn is the electron mobility
The holes acquires a drift velocity Vp−drift
Vp−drift = μp E μp is the hole mobility
The free electrons acquires a drift velocity Vn−drift
Vn−drift = −μnE μn is the electron mobility
The holes acquires a drift velocity Vp−drift
Vp−drift = μp E μp is the hole mobility
The drift of the charge carriers produces Drift current Idrift
Holes Drift current Ip
Holes Drift current Ip
Consider a plane perpendicular to electric field direction with cross-sectional area A