The History of Semiconductor Heterostructures Reserch:

from Early Double Heterostructure Concept to Modern Quantum Dot

Structures

Zhores Alferov

St Petersburg Academic University —Nanotechnology Research and Education Centre RAS

2

• Introduction• Transistor discovery• Discovery of laser-maser principle

and birth of optoelectronics• Heterostructure early proposals• Double heterostructure concept: classical,

quantum well and superlatticeheterostructure.“God-made” and “Man-made” crystals

• Heterostructure electronics• Quantum dot heterostructures and

development of quantum dot lasers• Future trends in heterostructure technology• Summary

3

The Nobel Prize in Physics 1956"for their researches on semiconductors

and their discovery of the transistor effect"

William Bradford Shockley1910–1989

John Bardeen1908–1991

Walter Houser Brattain1902–1987

4

5

6

7W. Shockley and A. Ioffe. Prague. 1960.

88

The Nobel Prize in Physics 1964

"for fundamental work in the field of quantum electronics, which has led to the construction of oscillators

and amplifiers based on the maser-laser principle"

Charles Hard Townes

b. 1915

NicolayBasov

1922–2001

Aleksandr Prokhorov

1916–2002

99

10

• N. Basov, O. Krochin and Yu. Popov(Lebedev Institute, USSR Academy of Sciences, Moscow)JETP, 40, 1879 (1961)

• M.G.A. Bernard and G. Duraffourg(Centre National d’Etudes des Telecommunications, Issy-les-Moulineaux, Seine)Physica Status Solidi, 1, 699 (1961)

Proposals of semiconductor injection lasers

1111

• January 1962: observations of superlumenscences in GaAs p-n junctions(Ioffe Institute, USSR).

• Sept.-Dec. 1962: laser action in GaAs and GaAsP p-n junctions(General Electric , IBM (USA); Lebedev Institute (USSR).

Condition of optical gain: EnF – Ep

F > Eg

Lasers and LEDs on p–n junctions

WavelengthLi

ght i

nten

sity

“+”

“–”Cleaved mirror

pn

GaAs

EnF

EpF

EgLp

DLn

Dhν

1212

The Nobel Prize in Physics 2000"for basic work on information and communication technology"

Zhores I.Alferov

b. 1930

Herbert Kroemer

b. 1928

Jack S.Kilby

1923–2005

“for his part in the invention of the integrated circuit”

“for developing semiconductor heterostructures used in high-speed- and opto-electronics”

13

14

circuit

15

16

17

Fundamental physical phenomena inclassical heterostructures

(a)

(b)

(c)

Fn

Ec

∆Ev

∆Ec

Fp

Electrons

Holes

Fn Ec

Ev

Fp

Electrons

Holes

Electrons

One-side InjectionPropozal — 1948 (W. Shokley)Experiment — 1965 (Zh. Alferov et al.)

SuperinjectionTheory — 1966 (Zh. Alferov et al.)Experiment — 1968 (Zh. Alferov et al.)

Diffusion in built-inquasielectric fieldTheory — 1956 (H. Kroemer)Experiment — 1967 (Zh. Alferov et al.)

18

(d)

(e)Ec

Ev

FnEc

Ev

Fp

Electron and optical confinementPropozal — 1963 (Zh. Alferov, R. Kazarinov)

(H. Kroemer)Experiment — 1968 (Zh. Alferov et al.)

SuperlatticesTheory — 1962 (L.V. Keldysh)Experiment —1970 (L. Esaki et al.)Stimulated emission:Theory — 1971 (R. Kazarinov and R. Suris)Experiment —1994 (F. Capasso et al.)

Fundamental physical phenomena inclassical heterostructures

19

Long journey from infinite interface recombination to ideal heterojunction

Lattice matched heterojunctions

• Ge–GaAs–1959(R. L. Anderson)

• AlGaAs–1967(Zh. Alferov et al., J. M. Woodall & H. S. Rupprecht)

• Quaternary HS (InGaAsP & AlGaAsSb)Proposal–1970 (Zh. Alferov et al.)First experiment–1972 (Antipas et al.)

Heterojunctions—a new kind of semiconductor materials:

5.40 5.56 5.72 5.88 6.04 6.20Lattice constant ( ) [300 K]Å

Ene

rgy

gap

(eV

) [30

0 K

]

2.8

2.0

1.2

0.4

AlP

GaP

GaAs

Ge

InPAlSb

GaSb

InAs

20

Radiation spectrum for the first low threshold AlxGa1–xAs DHS laser at room temperature

Rad

iatio

n in

tens

ity (a

rb. u

nits

)

1.59 eV1.61 eV

(2)

1.59 eV

1.39 eV

×100

(3)

1.61 eV(1)

7100 7700 8300 8900Wavelength ( )Å

7760 7820

(2)

(1)

Wavelength ( )Å

(a)

(b)

300 K = 4300 A/cmJth

2

21

Schematic representation of the DHS injection laser in the first CW-operation

at room temperature

250 µm

120

µm

200 mA

Copper

Metal

Metal

SiO2

p Al Ga As 3 µm0.25 0.75

p Al Ga As 3 µm0.25 0.75

p GaAs 0.5 µm

p GaAs 3 µm+

n GaAs

22

Space station “Mir” equipped with heterostructure solar cells

Heterostructure solar cells

23

Heterostructure microelectronicsHeterojunction Bipolar Transistor

NAlGaAs-n GaAs Heterojunction

Suggestion—1948 (W.Shockley)Theory—1957 (H.Kroemer)Experiment—1972 (Zh.Alferov et al.)AlGaAs HBT

HEMT—1980 (T.Mimura et al.)

Speed-power performances

J–J

100 nW 1 µW 10 µW 100 µW 1 mW 10 mW

10 ns

1 ns

100 ps

10 ps

Pro

paga

tion

dela

y

Power dissipation

∆Ec

Ev

Ec

∆Ev

F

F

∆Ec

Ev

EcE1

E0

∆Ev

24

(by I. Hayashi, 1985)Heterostructure Tree

HighPower

ElectronicsLD

LED

APDPIN

DetectorArray

FET

HEMTHBT

GaAsIC

HSSolarCell's

PhasedArrayLD

Multi-Wavelength

LDPIN-FETLD-Driver

One ChipRepeater

MonolithicOEICSwitch Optical

ConnectionBetween

LSIsOpticalWiringInside

LSISSI

MSI

LSIIntegrationof Optical

and ElectronicDevices

Integrationof OpticalDevices

Integration ofBifunctional

Devices

Wide BandOptical Transition

Wavelength DivisionMultiplexity

All Optical Link

Laser DiskLaser Printer

Optical Sensor

Advanced LAN

BidirectionalVideo Network Super High Speed

Computer

One ChipComputer

IntegrationTechnology

Device Technology

ProcessTechnology

SubstrateCrystal

EpitaxiThin Film

MaterialCharacterization

25

Impact of dimensionality ondensity of states

Lz

Lx

Lz

3D

0D

1D

2D

Ly

LzLx

Egap

E00 E01

E0 E1

E000 E001

Den

sity

of s

tate

sP

N

P

N

P

N

P

N

Energy

26

Temperature dependence of the normalized threshold current

for different DHS lasers

(a) Bulk

(b) Quantum well

(c) Quantum wire

(d) Quantum dot

(d)

(c)

(b)

(a)(a) = 104 °CT0(b) = 285 °CT0(c) = 481 °CT0(d) = T0 ∞

–60 –40 –20 0 20 40 60Temperature (°C)

1.5

1.0

0.5

Nor

mal

ized

thre

shol

d cu

rren

t Jth— Jth =

— J Tth( )Jth(0) T

T0

= exp

27

Stranski–Krastanow growth mode

• High surface energy of the substrate — thin wetting layer

• High surface energy of the film — 2D growth

• High strain energy of the film — 3D Clusters

Frank–van der Merve Volmer–Weber Stranski–Krastanow

28

Cross-section of high resolution electron micrograph image of a single quantum dot for 3-ML InAs deposited; arrows indicate the boundary facets.

2 nm

001

100

29

Cross-section TEM image of MBE-grown laser with InGaAs-AlGaAs QDs

Cladding layers are grown at 700 °CHigh power operation up to 1W CW

20 nm

Al Ga As matrix0.15 0.85

2 nm Al Ga As–1 nm GaAs×50 SL

0.3 0.7

2 nm Al Ga As–1 nm GaAs×47 SL

0.3 0.7

InGaAs

Vertically coupledquantum dots

Ts = 480°C

30

Vertical-Cavity Surface-Emitting Lasers

Edge Emitting Laser

Vertical Cavity Surface Emitting Laser

(VCSEL)

VCSELs:• Ultralow threshold current• High beam quality• Monolitically-integrated mirrors

Planar technology, on-wafer testing, dense arrays, on-chip integration140% annual market growth. Need in reliable 1.3 & 1.55 µm VCSELs, in UV VCSELs

31

Band diagram Layer sequence

Emission spectrum at room temperature

Light- and Volt-currentcharacteristics

Pulsedroom temperature

8.5 8.6 8.7Wavelength, µm

Opt

ical

pow

er (l

og.,

a.u.

) 1

0.1

0.01

0.001

8K

150K

200K

250K

Current, A

Pow

er, m

W

Volta

ge, V

12

0

4

8

80

60

40

20

00 0.5 1.0 1.5

Quantum cascade lasers

32

• Evolution and revolutionary changes• Reduction of dimensionality results in improvements

Milestones of semiconductor lasers

4.3 kA/cm(1968)

2

900 A/cm(1970)

2

160 A/cm(1981)

240 A/cm

(1988)2

6 A/cm(2002)

2

19 A/cm(2000)

2

Impact of SPSL QW

105

104

103

102

10

01960 00 200565 70 75 80 85 90 95

Years

J th

2 (A

/cm

)Impact of DoubleHeterostructures

Impact of Quantum Wells

Impact of Quantum

Dots

33

“Magic Leather” energy consumption

200 000

150 000

1 000 000

90 000

1 440 000

15 000 000

Energy Carrier

Total throughout the worldReserves(known andextractive)

(GWatt year)×

Consumptionrate

(GWatt)

Period ofexhaust

(years)

Oil

Gas

Coal

Nuclear Power(thermal reactors)

Total

Nuclear Power(fast reactors)

4 600

2 200

3 000

750*

11 000

11 000*

40–50

60–70

300–400

120

130

1 500

*Calculated value

34

5

10

15

20

25

30

35

40

45

1950 1960 1970 1980 1990 2000 2010 2020

III-V ConcentratorMulti-junction

Concentrator AlGaAs/GaAs

Single-junction

Cryst. Si“one-sun”

Thin-Film Si

Year

50

Concentr. Si

Effi

cien

cy (%

) of s

olar

ene

rgy

conv

ersi

on

The evolution of achieved in the world till 2006 and predicted efficiencies of solar cells based on

III-V semiconductors

35

Mirrors, large cells, heat pipes (early 1980s)

The tendency in concentrator PV: from large to small concentrators at high concentration ratio!

Concentrator PV installations at the Ioffe Institute

Fresnel lenses, medium cells (middle of 1980s)

Smooth lenses, small cells (late 1980s)

36

Multijunction solar cells provide conversion of the solar spectrum with higher efficiency. Achievable efficiency of multijunction cells is > 50%

SiGaInP GaAs

Ge

200400600800

1000120014001600

200400600800

1000120014001600

0 0500 1000 1500 2000 2500 500 1000 1500 2000 2500

Wavelength (nm) Wavelength (nm)

Spec

tral i

rrad

ianc

e (W

/m µ

m)

2

37

The theoretical limit for MJ cells

• Calculation made in the radiative limit

• Calculated for the concentration limit

• Optimum band gaps assumed 0 1 2 3 4 5 640

45

50

55

60

65

70

75 46200 x 850 W/m² AM1,5d = 333 KT

Number of pn-junctions

Effi

cien

cy (%

)

38

140

120

100

80

60

40

20

0

Inst

alle

d ca

paci

ties

(GW

)

2000 2010 20202030Year

USAEuropeJapanWorld

Evolution of the solar electrical capacities till 2030 year

39

Yes!

Is Solar Energy Conversion an Option to Solve the Energy Problems

in Future?

4040

White light-emitting diodes:efficiency, controllability, reliability, life time

Today:InGaN-QW/GaN/sapphirelight-emitting chip + YAG Ce phosphor

Outlook:Monolithic microcavity LED with InGN/GN MQW active region

+ simple design– phosphor loss

+ monolithic nature+ absence of additional loss

WhitePhosphor YAG Ce

Sapphire

Buffer

n+GaN

InGaN-QW

p+GaN

Ti/Ag/AuNi/Ag/Au

White

Sapphire

Buffer

n+GaN

Ti/Ag/Au

InGaN-QW

p+GaN

Ni/Ag/AuBragg resonator GaN/AlGaN

4141

Nanostructures for high power semiconductor lasers

Laser array output power > 100 WMatrix output power > 5 kW

Laser efficiency > 75%Laser power > 10 W

5 nm

Band gap, eV

Thic

knes

s, n

m

Solid-state lasers pumping

Atmospheric and fibre optical

communication

Navigation

Energy transport in the atmosphere

and fibre

Welding and cutting

Atmospheric lidars

Medical apparatus

Fibre lasers

42

1. Heterostructures — a new kind of semiconductor materials:• expensive, complicated chemically & technologically but most efficient2. Modern optoelectronics is based on heterostructure applications• DHS laser — key device of the modern optoelectronics • HS PD — the most efficient & high speed photo diode• OEIC — only solve problem of high information density of optical

communication system3. Future high speed microelectronics will mostly use

heterostructures

4. High temperature, high speed power electronics —a new broad field of heterostructure applications

5. Heterostructures in solar energy conversion:the most expensive photocells and the cheapest solar electricity producer

6. In the 21st century heterostructures in electronics will reserve only 1% for homojunctions

Summary