IFE T&CS

Semiconductor Devices

Chapter 5

Power devices

Prof. Zbigniew Lisik

room: 116

e-mail: zbigniew.lisik@p.lodz.pl

Department of Semiconductor and

Optoelectronics Devices

Power Devices

Chapter 5

Power devices - overview

Basic features :

● main application – switches in DC and

AC circuits

● large dimensions

● cooling requirement

● large price of a single device

Power Devices

Chapter 5

Power devices - overview

Basic requirements :

● large forward current : typically 40 - 1000 A, max. 6 kA

● large blocking voltage : typically 300V - 2kV, max. 10 kV

● large switching frequency : for bipolar > 10 kHz

for unipolar > 100kHz

● low losses in on-state : min (UonIon)

● simple control solutions : small control power

Power Devices

Chapter 5

Bipolar

Diodes

Bipolar

Transistors

Thyristors

GTO

Unipolar

MOSFET

Transistors

JFET

Transistors

BiMOS

Isolated Gate

Bipolar Tranzystors

(IGBT)

Static Induction

Thyristor (SITh)

Power devices - overview

Power Devices - Thyristor

Chapter 5

Thyristor principle

It is 3 terminal device that has been created by the integration of well know

circuit of, so called, TT latch –up (switch)

G

A

K

n

n

p

p

A

K

G

IA

T1

T2

IG

IK = IA + IG

● n-p-n-p structure

● four layers

● three junctions

● three electrodes:

A – anode

K – cathode

G – gate

Power Devices - Thyristor

Chapter 5

Work principle

G

A

K

n

n

p

p

A

K

G

IA

T1

T2

IG

IK = IA + IG

● reverse bias - UAK < 0, device

can block only,

● forward bias - UAK > 0, device

blocks the voltage but it can

be turned into on-state (large

anode current IA at low

voltage drop),

● device is controlled by the

gate current IG that can turn–on it at forward bias,

● in ordinary thyristors, the reverse gate current cannot turn-off them,

it is possible in designed in special way GTO thyristors, only.

Power Devices - Thyristor

Chapter 5

Turn-on process

A

K

G

IA = IE2

IC1 = IB2

T1

T2

IC2

IB1 IG

IK = IE1

UAK

IT

● blocking state: UAK= Uext > 0,

IG = 0, IA = 0

● start of turn-on : UAK= Uext > 0,

IG= IG0 > IGmin, IC1= IC2= 0 IA = 0

● transient process – positive

feedback: IA = IC1 + IC2

IB1 = IG = IG0 IC1 = 1IG0

IB2 = IC1= 1IG0 IC2 = 2IB2 = 12IG0

I’B1 = IC2 + IG0 I’C1 = 1I’B1 = 1 (IC2+IG0)

I’B2 = I’C1 = 1 (IC2+IG0) I’C2 = 2I’B2 = 12(IC2+IG0)

I’’C1= …..I’’C2= …...

Power Devices - Thyristor

Chapter 5

Turn-on process

A

K

G

IA = IE2

IC1 = IB2

T1

T2

IC2

IB1 IG

IK = IE1

UAK

IT

● blocking state: UAK= Uext > 0,

IG = 0, IA = 0

● start of turn-on : UAK= Uext > 0,

IG= IG0 > IGmin, IC1= IC2= 0 IA = 0

● transient process – positive

feedback: IA = IC1 + IC2

IB1 = IG = IG0 IC1 = 1IG0

IB2 = IC1= 1IG0 IC2 = 2IB2 = 12IG0

● turn-on state: IG = 0 IG = 0,

IA = IK UAK= UT = 1,6 ÷ 2 V

I’C1= …..I’C2= …...

Power Devices - Thyristor

Chapter 5

Gate turn-on

t

t

t

IT

IA

0.1UD

0.9UDUDM

UAK

0.1IGM

IGM

IG

tG

trtd

IGM – gate current amplitude

UD – blocking voltage

IT – thyristor forward current

tG – duration of the gate current

pulse

td – delay time

tr – rise time

ton = td + tr

Power Devices - Thyristor

Chapter 5

Forced turn-off

● forced turn-off circuit

td

E

t

RIT

UT

Th

E

td – disposal time – determined by the external circuit

Power Devices - Thyristor

Chapter 5

Forced turn-off

● Turn-off process

td

E

t

R

IT

UT

Th

E

tq – turn-off time – determined

by the phenomena taking place

in the semiconductor structure

leading to the recovery of

voltage blocking ability

IT

tq

UT

Power Devices – Field control transistors

Chapter 5

Descended from JFET idea

● Static Induction Transistor SIT (unipolar)

Burried

gate

construction

S

D

G

n+

n+

n-

p+

The SIT design

copies the idea

of electron tube

called „triode”

Power Devices – Field control transistors

Chapter 5

Descended from JFET idea

● Static Induction Thyristor SITh (Bi-MOS)

Emitter

junction

K

A

G

n+

p+

n-

p+

The SITh design

copies the idea

of electron tube

called „triode”

Power Devices – Field control transistors

Chapter 5

Descended from MOSFET idea

● Vertical MOS VMOS (unipolar)

One cell of

multicell device

thousands of

cells

D

pn

n-

n+

GS

n

S

Uniformity of MOS cells is

preserved due to the

uniformity od dry eaching

process

Power Devices – Field control transistors

Chapter 5

Descended from MOSFET idea

● Vertical Double Diffusion VDMOS (unipolar)

One cell of

multicell device

thousands of

cells

Uniformity of MOS cells is

preserved due to the

uniformity of double diffusion

process (one mask approach)D

n-

n+

p n

GS S

n

Power Devices – Field control transistors

● CoolMOS (unipolar)

Część 5

Descended from MOSFET idea

One cell of

multicell device

thousands of

cells

Uniformity of MOS cells is

preserved, among others,

due to the uniformity of

double diffusion process

(one mask approach)

Power Devices – Field control transistors

Chapter 5

Descended from bipolar transistor idea

● Integrated Gate Bipolal Transistor IGBT (Bi-MOS)

G

S

D

D

n-

n+

p+

n

G S

n

G Basing MOS

structure

Power Devices – Field control transistors

Chapter 5

Descended from bipolar transistor idea

● Integrated Gate Bipolal Transistor IGBT (Bi-MOS)

Modified MOS

structure

IGBT structure

C

n-

p+

p+

n

G E

n

G

G

E

C

Power Devices - IPM

Chapter 5

IPM – Inteligemt Power Module