new trends and challanges in crystal growth in scientific ... · 15th inter national summer school...

15th International Summer School on Crytsal Growth – ISSCG-15

New trends and challanges in crystal

growth in scientific and commercial

aspects (semiconductors world)

Mike Leszczynski Institute of High Pressure Physics UNIPRESS

And

TopGaN Lasers, Ltd.

Warsaw, Poland

[email protected]

15th Inter national Summer School on Crystal Growth – ISSCG-15 LESZCZYNSKI MIKE

Abstract

The presentation shows two main new semiconductors: GaN and SiC which

are and will be revolutionizing many areas of the everyday life and

technology. GaN-based optoelectronic devices: white LEDs, laser diodes

emitting from uv to green will soon form new markets of laser tv, „last mile”

telecommunication, water purification, bio-hazardous material detection,

and many others. Both, GaN- and SiC-based electronic devices will replace

many based on silicon, allowing to achieve higher frequencies and power of

transistor operation.

Unfortunately, both GaN and SiC materials are very difficult to be grown

because of their high metling points and other thermodynamic properties. It

will be shown, how lateral patterning helps to overcome many problems with

crystallographic quality of the substrates and the epi-wafers.

Special attention will be paid to the GaN and SiC off-cut substrates, what

changes significantly the properties of the epi structures grown on them.


Unipress and TopGaN

One of the largest European group involved in research

on GaN-based semiconductors

60 scientists, bulk GaN growth, 9 epitaxial systems, laser

diode processing

15 EU Projects, 10 National Projects on Nitride

Semiconductors

Many patented and proprietary technologies


Some pictures from Unipress/TopGaN lab


Semiconductor device markets

Based on Si: around Eur 90 billion OLD TREND

On GaN: around Eur 15 billion NEW TREND

On GaAs: around Eur 5 billion OLD TREND

On SiC: around Eur 0.5 billion NEW TREND

On graphene: to be NEW TREND (shown by Jacek

Majewski)


Main properties of semiconductors

GaAs, GaN – direct band gap

Si, SiC- indirect (low efficiency of optoelectronic devices)


Outline

Main new markets

GaN technology (presentation in collaboration with TopGaN

and Unipress)

SiC technology (presentation in collaboration with SiCrystal,

NovaSiC and LPE- Partners in EU LAST POWER project)

Some technological issues

Growth on prepatterned substrates

Off-cut substrates

Elimination of structural defects

Growth of ternary substrates

Large wafers


GaN technology

Applications

Present: White LEDs and BluRay

Future: RGB projectors, „Last mile” communication, car

headlights, high-frequency/high-power electronics

Growth on foreign substrates

GaN bulk substrates

Growth on off-cut GaN substrates

Growth of InGaN quantum wells


Amano and Akasaki (Meijo

University)

At the end of 80-ties of XX

century:

Growth on sapphire

P-doping

Shuji Nakamura (Nichia)

First commercial blue LEDs 1992

First LDs 1996

Strong Japanese domination in GaN technology

15th Inter national Summer School on Crystal Growth – ISSCG-15 LESZCZYNSKI MIKE 10

WHITE LEDs

Biggest manufacturers:

Nichia (Japan), OSRAM

(Germany), Lumileds, Cree

(USA)

Market in 2020: Eur 30-60 bln


BluRay based on 405 nm laser diodes Manufacturers:

Nichia

Sony

Sanyo

Matsushita

(Japan),

100 Mln pcs in 2012

No further growth

Decrease soon!


Painting (color projection) should be done using clean paints

In plasma TV, LED TV, color filtering, we „paint” with „dirty” R&G&B emitters


Only Laser Projection can give a

color resolution like in Nature


Laser projectors:

Pico

Cinema

Television

3D possible without goggles!!!


„Last mile” Tbit/sec communication with

plastic fibres and 480-500 nm laser diodes

Buildings

Cars

Airplanes

Ships

http://www.google.pl/url?sa=i&source=images&cd=&docid=o5e3vzPbqoGMcM&tbnid=c2UkZlk4qBCnKM:&ved=0CAgQjRwwAA&url=http://blog.tomevslin.com/2007/02/television_on_t.html&ei=JiCCUYXFBIqTsway24DwCQ&psig=AFQjCNHfNz5NZXaJ4wYpYh51IbAVbAm2xw&ust=1367568806115218


GaN-based semiconductors:

Much more difficult to be grown than

Si, GaAs, InP

Melting point: Above 2800 K, 60 kbar

No growth from the melt

Decomposition at 1 bar:

GaN around 1300 K

InN around 800 K


Almost all LED GaN-based structures are grown

on sapphire or silicon

Dislocation density of about 5x109 cm-2


Trick with LT

buffer layer


For laser diodes, it is necessary to have a lower

dislocation density

S. Uchida et al. Sony

Shiroishi Semicond. Inc

IEEE J. of Selected Topics in

Quantum Electronics 9, no 5,

(2003)1252.

Our data


SUMITOMO- leader in GaN substrate growth

http://global-sei.com/news/press/10/10_25.html


Ammonothermal growth

2-inch

n-type do 2x1019 cm-3

p-type,

TDD=5x104 cm-2

R=100 m


HVPE + HNP – combined method of TopGaN

High Nitrogen

Pressure Overgrowth

Hydride Vapour Phase Epitaxy:

Fast growth, large dimensions

+

15th Inter national Summer School on Crystal Growth – ISSCG-15 LESZCZYNSKI MIKE 1.5 inch HNPS-GaN 330 µm T

t=500 h

a b c

nowo wzrośnięty

HNPS-GaN

GaN substrates from

Multi-feed-seed-method

10 kbar, 1600oC, growth from N solution in

Ga


GaN-based laser diodes- main issues

p- doping InGaN QWs- In-segregation, electric built-in fields AlGaN- cladding, lattice mismatch Bulk GaN substrate


Laser diode epitaxial structure: TEM topograph


Lattice mismatch Green gap

Electric field

In segregation in InGaN

P-doping And others!!!

Droop

Problems in GaN technology

holes

electrons


Elimination of

cracking and

bowing

No AlN mask

With AlN mask 15 10 5 3 m

Defect density: window <106/cm2 mask 1010/cm2

AlGaN 27% 220 nm


Motivation of using off-oriented substrates:

Better/different electrical, optical, structural,

morphological, properties of AlGaN, InGaN, InAlN

Cutting/polishing- expensive Lateral patterning

(patented)


Misorientation of 0.5-1 degree desired because of better morphology

AFM- GaN layers grown at high temperature

Misorientation: 0.2 degree 0.6 degree

Higher misorientation (above 1 degree): step condensation


P-doping

Hole concentration in GaN:Mg I-V LD characteristics No difference in Mg and H concentration (SIMS)

0 5 10 15 20

0

1

2

3

4

5

6

7

8

9

10

laser

diod

e vo

ltage

[V]

current density (kA/cm2)

miscut 1 deg

miscut 0.2 deg

0,0 0,5 1,0 1,5 2,0 2,50,0

5,0x1017

1,0x1018

NT1388

Ho

le c

arr

ier

co

nce

ntr

atio

n

p [

cm

-3]

Misorientation angle [deg.]


Morphology of InGaN layers grown on GaN substrates of different misorientation, Tgrowth = 820oC

0.2 degree 0.8 degree 1.8 degree


In incorporation into InGaN layers versus

GaN substrate misorientation

Lower indium incorporation into InGaN for

off-oriented GaN substrate


The same mechanism as in indium incorporation into

InGaN versus growth rate in step-flow mode


Lateral patterning to vary the misorientation across

the wafer- multicolour arrays of laser diode stripes

12 nm difference in lasing


InGaN growth very difficult

Active region of all optoelectronic devices

emitting in visible region

Low growth temperature and large lattice

mismatch:

Point defects (including oxygen)

Indium segregation

3D growth

Mismatch defects (dislocations, pits)


In content – 14%

In content – 18%

In content – average 22%

420 440 460 480 500 520 540

0.0

0.2

0.4

0.6

0.8

1.0

no

rma

lize

d in

ten

sity

[nm]

TGR

= 800oC

TGR

= 770oC

TGR

= 730oC

TGR=800oC : =455nm fwhm=27nm



XRD:

31 32 33 34 35 36 37 38

1

10

100

1000

10000

100000

1000000

inte

nsity [

a.u

.]

2theta [deg.]

TGR

=800oC

TGR

=770oC

TGR

=730oC

PL- Photoluminescence (He-Cd laser 325 nm, cw):

QW growth temperature


XRD

Hydrogen effectively removes In and widens QBs

but also affects QWs:

removes In and makes them narrower.

0 10 20 30 402

3

4

5

6

7

8

9

10

11

12

13

14

15

QW

QB

wid

th [nm

]

H2 [%]

0 10 20 30 400

1

2

3

4

5

6

7

8

9

10

11

12

13

14

QW

QB

In [%

]

H2 [%]

Influence of H2 during QB growth


T=905oC In – 16%

=463nm

At high temperature satellite peaks becomes much more broader and

disappear :

QWs degradation occurs

T=880oC In – 18%

=463nm

T=830oC In – 18%

=463nm

T=930oC In – ?

=463nm

PL intensity decrease 31 32 33 34 35 36 37 38

0,1

1

2theta/ [deg.]

inte

nsity [

a.u

.]

Motivation: QWs must be overgrown with p-type layers

commonly fabricated at high temperatures

TGr of p-type layers

P-type growth


Electronics

High Electron

Mobility Transistors

(HEMTs)

based on 2DEG

Sensors of liquids

and gases


GigaHertz and TeraHertz area


THz emitters and detectors

0 10 20 30 40 50 60 700

10

20

30

40

50

60

70

80

90

X Axis (mm)

Y A

xis

(mm

)

0

0.02100

0.04200

0.06300

0.08400

0.1050

0.1260

0.1470

0.1680

0.1890

0.2100

Control of

water in

plants

Quality control in

manufacturing


GaN and SiC electronics:


GaN GHz and THz

Electronic devices by power and frequency


SiC technology

Applications in SiC electronics

Growth of SiC crystals

SiC epitaxy

GaN epitaxy on SiC crystals


It is difficult

to grow SiC

crystal without

polytyping

And more than 240 others!!!


It is even more difficult to grow SiC crystal

without micropipes

1) open core super screw

dislocations that propagate

along the C-axis from the

seed crystal during growth .

2) Contaminant particles

introduced during the growth

process


One of possible

mechanisms of

micropipe formation

(after MaxMile

Technologies)


Philip G. Neudeck and J. Anthony Powell

For many years, micropipes have been a main

obstacle in development of SiC based power

electronics


Quality results: Seed 155mm

High crystalline quality of 155 seed SiC shown by low FWHM close to equipment resolution. Next step: Increase diameter to 160mm.

2013: CREE and SiCrystal manufacture 6 inch SiC

substrates with no micropipes!!!

~ ~ FWHM = 13.61 arcsec

High resolution X-ray

diffraction

Crossed

polarizers

MPD

mapping 2 deg-off – a new standard for SiC epitaxy?

So far 4 deg off and 8 deg off.


Substrate from SY SiC 4” – 4H – 2°off Si-face CMP (Novasic), C-face optical polished

LPE: 2° off epi Optimization on 4’’ SiC 4H wf

– Mosfet Spec

- Lower epi stacking faults

(ESF) defects density (< 1,7 vs.

4.9 cm-2)

- high percentage of area free of

defects was (95,6%).

- low epi roughness (0,7 nm)

has been reached even in some

region is still high (2.8 -1,5 nm).

- Better epi thickness uniformity

(± 1,5%)

- Worse epi doping uniformity

was observed (15-22% VS USL

10%).

- some striped epi surface


2 deg off SiC substrates

Common platform for SiC-based devices

and GaN-based devices

1.Monolithic integration

2. Cheaper SI SiC substrates (conductive

SiC substrate with insulating homoepitaxial

layer) for high-frequency HEMTs based on

GaN


AlN

GaN undoped

1.5 um

AlN 1nm

AlGaN 20 nm

Cap GaN 2nm

SiC

TG2136 0°-off

TG2134 1°-off

TG2135 2°-off

XRD: TG2134 – Al0.22

GaN, 22 nm

TG2135 – Al0.21

GaN, 22 nm

TG2136 – Al0.21

GaN, 21 nm

HEMT wafers on off-cut SiC

32 33 34 35 36 37

100

101

102

103

104

105

106

HEMT on SiC

inte

nsity [cp

s]

2theta [deg]

0o offcut, tg2136

1o offcut, tg2134

2o offcut, tg2135


Comparison of roughness for HEMT epi-

structures for various off-cut of SiC substrates

Ra = 0.19 nm 0.77 nm 1.08 nm

AFM scans 3x3 mm2

Dislocation density 108 cm-2 (can be lower for off-cut substartes, but

in that case, roughness larger

0 deg 1 deg 2deg off


Electrical parameters of HEMT epi

wafers on off-cut SiC substrates

Off-cut

(deg)

n (1013cm-

2) Hall

(cm2/Vs)

Hall

(W)

0 1.26 1280 365

1 1.4 1323 332

2 1.03 1413 429

No significant difference in electrical parameters


Concluding remarks

1) GaN and SiC single crystals and epi-wafers pave the

way to a number of new markets:

Electric cars

Gigahertz and terahertz emitters and detectors

Laser TV, picoprojectors, cinema, telebeams, also 3D!!!

„Last mile” communication

And many others...

2) (AlGaIn)N and SiC are still in the infancy stage of

development, as they are very difficult to be grown,

processed and examined.

new trends and challanges in crystal growth in scientific ... · 15th inter national summer school...

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