Semiconductors and DiodesInstructor: Chao-Ching Ho ChaoNational Yunlin University of Science and Technology

Robotic Embedded System Lab

KVL 0

KCL

P =VI =I2R

REQ = R1 + R2 + K + RNRk Vk = Vs R1 + R2 + K + Rk + K + RN

REQ =

1 1 / R1 + 1 / R2 + K + 1 / RN

1 / Rk Ik = Is 1 / R1 + 1 / R2 + K + 1 / Rk + K + 1 / RN

()()

(doping) N(-) P(+)

ReferenceRizzoni : 5th Edition, Chap 9 (), Chap 2

Bohr model of an atomAs seen in this model, electrons circle the nucleus. Atomic structure of a material determines its ability to conduct or insulate.

Covalent Bonding ( )Covalent bonding is a bonding of two or more atoms by the interaction of their valence electrons.

The process of creating N- and P-type materials is called doping.Other atoms with 5 electrons such as Antimony () are added to Silicon to increase the free electrons. Other atoms with 3 electrons such as Boron () are added to Silicon to create a deficiency of electrons or hole charges.

N-type

P-type

Electric field in a pn junction

Wiley/Razavi/Fundamentals of Microelectronics

N P N()P ()()(Fig 9.5) P-N

(drift) Is ; (diffusion) Id ()

Fig. 9.5

p-n Junction & Diode

Offset voltage: V

The Depletion Region ()

250C 0.6V

(barrier potential)

Depletion zone to insulating stateAt the junction, free electrons from the N-type material fill holes from the P-type material. This creates an insulating layer in the middle of the diode called the depletion zone.

How To get rid of the depletion zone?

When the negative end of the circuit is hooked up to the Ntype layer and the positive end is hooked up to P-type layer, electrons and holes start moving and the depletion zone disappears.

When the positive end of the circuit is hooked up to the Ntype layer and the negative end is hooked up to the Ptype layer, free electrons collect on one end of the diode and holes collect on the other. The depletion zone gets bigger.

PN +N - P +P- N

(rectifier diode)

Wiley/Razavi/Fundamentals of Microelectronics

Fig. 9.9

Forward & Reverse biased diode equation Fig. 9.7, Eqn 9.6 id = I d I 0 = I 0 (e qv / kT 1)D

Dominant current: drift

Dominant current: diffusion

PN junction under reverse and forward bias.

Wiley/Razavi/Fundamentals of Microelectronics

Overall i-v characteristic of a diode Fig. 9.10

(Zener Diode)

Open (nA)

Constant-voltage diode model.

Reverse breakdown characteristic

Wiley/Razavi/Fundamentals of Microelectronics

(breakdown)

1A (1A)1N4003 1N4005 1N4005 1N4005 1N4005 1N4006 1N4007

(V)

50

100

200

400

600

800

1000

3A (3A)1N5400 1N5401 1N5402 1N5403 1N5404 1N5407 1N5408

(V)

50

100

200

400

600

800

1000

(Ideal Diode Model) Fig. 9.11

Fig 9.12-14VD0 VD