Channelling Theory and Simulation Channelling Applications · 2015-07-20 · SPRITE Workshop 1...

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SPRITE Workshop 1 Channelling Theory and Simulation Channelling Applications The FLUX Code Katharina Lorenz 1 , Andrés Redondo-Cubero 1,2 , Peter Smulders 3 1 Instituto Superior Técnico, Portugal 2 Universidad Autónoma Madrid, Spain 3 Groningen University, The Netherlands SPRITE Workshop, IST, 18. May 2015

Transcript of Channelling Theory and Simulation Channelling Applications · 2015-07-20 · SPRITE Workshop 1...

Page 1: Channelling Theory and Simulation Channelling Applications · 2015-07-20 · SPRITE Workshop 1 Channelling Theory and Simulation • Channelling Applications • The FLUX Code Katharina

SPRITE Workshop 1

Channelling Theory and Simulation

• Channelling Applications

• The FLUX Code

Katharina Lorenz1, Andrés Redondo-Cubero1,2,

Peter Smulders3

1Instituto Superior Técnico, Portugal

2Universidad Autónoma Madrid, Spain

3Groningen University, The Netherlands

SPRITE Workshop, IST, 18. May 2015

Page 2: Channelling Theory and Simulation Channelling Applications · 2015-07-20 · SPRITE Workshop 1 Channelling Theory and Simulation • Channelling Applications • The FLUX Code Katharina

SPRITE Workshop 2

Outline

• Introduction:

- Rutherford Backscattering and Channelling (RBS/C)

- III-Nitrides

• Characterisation of III-N structures from 3D to 0D:

- 3D Thin films (crystal quality, strain, ion implantation damage,

lattice site location of dopants)

- 2D Quantum wells (crystal quality, strain)

- 1D Nanowires (mosaicity)

- 0D Quantum dots (crystal quality, strain)

• The FLUX Code

• Summary

Page 3: Channelling Theory and Simulation Channelling Applications · 2015-07-20 · SPRITE Workshop 1 Channelling Theory and Simulation • Channelling Applications • The FLUX Code Katharina

SPRITE Workshop 3

RBS

Concept

+ Mass perception (kinematic factor)

+ Concentration (x-section)

+ Depth resolution (stopping force)

Page 4: Channelling Theory and Simulation Channelling Applications · 2015-07-20 · SPRITE Workshop 1 Channelling Theory and Simulation • Channelling Applications • The FLUX Code Katharina

SPRITE Workshop 4

Ion-Channelling

Reduction of yield up to 98%

Lattice position of impurities

(interstitial or substitutional)

Sensitive to disorder,

lattice mismatch, strain, defects

etc.

“Channelling of energetic ions

occurs when the beam is carefully

aligned with a major symmetry

direction of a single crystal.”

[Lindhard 1965]

Page 5: Channelling Theory and Simulation Channelling Applications · 2015-07-20 · SPRITE Workshop 1 Channelling Theory and Simulation • Channelling Applications • The FLUX Code Katharina

SPRITE Workshop 5

Schematic of particle trajectories undergoing scattering at the

surface and channeling within the crystal. The depth scale is

compressed relative to the width of the channel in order to

display the trajectories.

Ion-Channelling

Page 6: Channelling Theory and Simulation Channelling Applications · 2015-07-20 · SPRITE Workshop 1 Channelling Theory and Simulation • Channelling Applications • The FLUX Code Katharina

SPRITE Workshop 6

Channelled ion

Ion backscattered at surface

Backscattering or dechannelling takes place when the

incident angle is higher than the critical angle for channelling.

Ion-Channelling – Critical Angle

Page 7: Channelling Theory and Simulation Channelling Applications · 2015-07-20 · SPRITE Workshop 1 Channelling Theory and Simulation • Channelling Applications • The FLUX Code Katharina

SPRITE Workshop 7

RBS-Channelling

3 0 0 4 0 0 5 0 0 6 0 0

0

5 0 0 0

1 0 0 0 0

1 5 0 0 01 .8

o

1 .4o

1 .0o

0 .8o

0 .6o

0 .4o

0 .2o

0 .0o

c h a n n e l b

ac

ks

ca

tte

rin

g y

ield

-2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0

0.2

0.4

0.6

0.8

1.0

min

no

rmaliz

ed y

ield

angle [deg.]

• Minimum yield: related with the crystal quality (blocked area).

• Half-width angle: related with the critical angle for channeling.

Page 8: Channelling Theory and Simulation Channelling Applications · 2015-07-20 · SPRITE Workshop 1 Channelling Theory and Simulation • Channelling Applications • The FLUX Code Katharina

SPRITE Workshop 8

Rutherford Backscattering /Channelling

Elemental depth profile

Compositional quantification

Interface and growth problems

No standards, non-destructive

Damage profile

Lattice defects

Amorphous layers

Strain in epitaxial films

Page 9: Channelling Theory and Simulation Channelling Applications · 2015-07-20 · SPRITE Workshop 1 Channelling Theory and Simulation • Channelling Applications • The FLUX Code Katharina

SPRITE Workshop 9

Shadowed fraction

substitutional

interstitial

interstitial

RBS/C Lattice Site Location

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SPRITE Workshop 10

Group-III Nitrides

3.1 3.2 3.3 3.4 3.5 3.60

1

2

3

4

5

6

7

AlGaN

InGaN

Ba

nd

ga

p (

eV

)

a Lattice Constant (Å)

AlN

GaN

InN

Al1-x

InxN x~17-18 %

Al1-x

InxN

InGaN:

LEDs, LASERS

AlGaN:

UV emitters/

Detectors

HEMTS

AlInN: - Widest energy range

- Lattice-match to GaN

Page 11: Channelling Theory and Simulation Channelling Applications · 2015-07-20 · SPRITE Workshop 1 Channelling Theory and Simulation • Channelling Applications • The FLUX Code Katharina

SPRITE Workshop 11

Samples

Al1-xInxN

- Growth by MOCVD

- Substrate: GaN on (0001) sapphire

- Thickness: ~100 nm

sapphire

GaN (1-6 mm)

Al1-xInxN

Biaxial strain

a

c

Page 12: Channelling Theory and Simulation Channelling Applications · 2015-07-20 · SPRITE Workshop 1 Channelling Theory and Simulation • Channelling Applications • The FLUX Code Katharina

SPRITE Workshop 12

Crystal Quality of thin films

300 400 500 600 7000

500

1000

1500

2000Al

Ga

random

fit

<0001> aligned

cou

nts

channel

In

min(In)=3%

Composition, thickness and crystal quality

Good crystal quality for InN contents < ~20% (Minimum yields 3-6%)

}

}

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SPRITE Workshop 13

Example AlInN/GaN bi-layers

350 400 450 500 550 600 650 7000

500

1000

1500

2000

25001000 1200 1400 1600 1800

Ga

In random

fit

<0001> aligned

min

(In)=0.04

co

un

ts

channel

Al

energy [keV]

400 6000

500

1000

1500

2000

1000 1200 1400 1600 1800

min

(In)=0.40

24%In random

Fit

<0001> aligned

cou

nts

channel

19%In

energy [keV]

w

w

Good crystalline quality Worse crystalline quality

Growth at 840 ºC Growth at 760 ºC

Page 14: Channelling Theory and Simulation Channelling Applications · 2015-07-20 · SPRITE Workshop 1 Channelling Theory and Simulation • Channelling Applications • The FLUX Code Katharina

SPRITE Workshop 14

Measuring Strain by RBS/C

cossin

||

rel

relepi

c

cc

rel

relepi

a

aa

||

Tetragonal distortion:

c

atan

Lorenz et al. PRL 97 (2006) 85501

Lorenz et al. JCG 310 (2008) 4058

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SPRITE Workshop 15

Strain Relaxation: Compressive Strain

400 500 600 7000

500

1000

1500

2000

1000 1200 1400 1600 1800

min

(In)=0.40

24%In random

Fit

<0001> aligned

co

un

ts

channel

19%In

energy [keV]

w

w

30.5 31.0 31.5 32.0 32.5 33.0

0.6

0.7

0.8

0.9

1.0

1.1

Ga

In interface

In surface

no

rmalis

ed y

ield

angle (deg.)

<-2113>

relaxed AlInN

Depth dependent strain measurement

Energy windows (W) select different depths

Surface layer is relaxed

Deeper region under compressive strain

Relaxation via change of composition

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SPRITE Workshop 16

Strain Relaxation: Compressive Strain

600 800 1000 1200 14000

500

1000

1500

Random

Fit

<0001> alignedco

un

ts

energy (keV)

min

(In)= 0.3

Al0.78

In0.22

N

W1 W2

-1.0 -0.5 0.0 0.5 1.0 1.50.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1.1

W1 (interface)

W2 (surface)

no

rma

lise

d y

ield

angle (deg.)

<2113>

Relaxation towards the surface

Relaxation via change of c/a ratio (constant composition)

Depth dependent strain measurement

Energy windows (W) select different depths

Page 17: Channelling Theory and Simulation Channelling Applications · 2015-07-20 · SPRITE Workshop 1 Channelling Theory and Simulation • Channelling Applications • The FLUX Code Katharina

SPRITE Workshop 17

Morphology Change

Pseudomorphic

x=.16

Partly relaxed

x=0.22

Relaxed

x=0.240.19

RMS=0.6 nm RMS=2.1 nm RMS=6.2 nm

Roughening/3D growth

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SPRITE Workshop 18

“Anomalous” features like double-dips

InN content 15%

30.5 31.0 31.5 32.0 32.5 33.0 33.50.0

0.2

0.4

0.6

0.8

1.0 <2113>

31.7º

Ga

In

no

rmaliz

ed y

ield

angle (deg.)

32.4ºR

100 200 300 400 500 600 7000

500

1000

1500

2000

2500

3000

random

aligned

min(In)=0.06

co

un

ts

channel

Al

Ga

In

R: angle for relaxed AlInN

determined from Vegard´s law

Page 19: Channelling Theory and Simulation Channelling Applications · 2015-07-20 · SPRITE Workshop 1 Channelling Theory and Simulation • Channelling Applications • The FLUX Code Katharina

SPRITE Workshop 19

Steering effects in the interface

Angular scan of GaN substrate distorted when kink angle ≤ critical angle

a-energy

kink angle (InN content)

InN content 19%

30.5 31.0 31.5 32.0 32.5 33.0 33.50.0

0.2

0.4

0.6

0.8

1.0

Ga

In

no

rmaliz

ed y

ield

angle (deg.)

<2113>

Page 20: Channelling Theory and Simulation Channelling Applications · 2015-07-20 · SPRITE Workshop 1 Channelling Theory and Simulation • Channelling Applications • The FLUX Code Katharina

SPRITE Workshop 20

Steering effects: FLUX Simulations

→ Increasing beam energy

→ Comparison with simulations

Different kink angles

-1.5 -1.0 -0.5 0.0 0.5 1.0 1.50.0

0.2

0.4

0.6 In 1 MeV

Ga 1 MeV

Ga 2 MeV

Yie

ldAngle (deg.)

º

-2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.50.0

0.2

0.4

0.6

0.8

Yie

ld

Angle (deg.)

AlInN

Ga =0.7º

Ga =0.4º

Ga =0.2º

Different energies

Redondo-Cubero, Lorenz et al. APL 95 (2009) 051921

Redondo-Cubero, Lorenz et al. JPD 42 (2009) 065420

Page 21: Channelling Theory and Simulation Channelling Applications · 2015-07-20 · SPRITE Workshop 1 Channelling Theory and Simulation • Channelling Applications • The FLUX Code Katharina

SPRITE Workshop 21

GaN Scans and FLUX Simulations

<-2113>

-1.5 -1.0 -0.5 0.0 0.5 1.00.2

0.4

0.6

0.8

1.0<10-11>

Angle [deg.]

N

orm

alis

ed Y

ield

-1.5 -1.0 -0.5 0.0 0.5 1.0

<10-11>

<-2113>

-1.5 -1.0 -0.5 0.0 0.5 1.0

<10-11>

0.2

0.4

0.6

0.8

1.0

1.2

experiment

simulation

13% InN15% InN

<-2113>

19% InN

=0.3º =0.5º =0.66º

Page 22: Channelling Theory and Simulation Channelling Applications · 2015-07-20 · SPRITE Workshop 1 Channelling Theory and Simulation • Channelling Applications • The FLUX Code Katharina

SPRITE Workshop 22

Strain Analysis XRD - RBS

||

XRD

RBS

cossin

0.12 0.13 0.14 0.15 0.16 0.17 0.18 0.19 0.20-0.8

-0.6

-0.4

-0.2

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

compressive

te

trag

on

al dis

tort

ion

T

[%]

RBS InN content x

XRD

RBS/C+MC

raw RBS/C

weighted linear fit

tensile

Lorenz et al. PRL 97 (2006) 85501 Perfect Lattice matching for x=0.171

Page 23: Channelling Theory and Simulation Channelling Applications · 2015-07-20 · SPRITE Workshop 1 Channelling Theory and Simulation • Channelling Applications • The FLUX Code Katharina

SPRITE Workshop 23

Implantation damage in GaN

31015 at/cm2 Eu implantation 300 keV at RT

2 damage regions (surface / bulk)

500 520 540 560 580 600 620 640 660 680 700 720

200

400

600

800

1000

1200

1400

1600

18001400 1500 1600 1700 1800

random

<0001> aligned

<0001> aligned virgin

channel

yie

ld (

coun

ts)

Eu

x10B

energy (keV)

S

Page 24: Channelling Theory and Simulation Channelling Applications · 2015-07-20 · SPRITE Workshop 1 Channelling Theory and Simulation • Channelling Applications • The FLUX Code Katharina

SPRITE Workshop 24

0 100 200 300 4000.00

0.02

0.04

0.06

0.08

min

depth (nm)

exp. min

1x1014

Ar/cm2

SRIM Argon profile

SRIM defect profile

0 100 200 300 4000.00

0.02

0.04

0.06

0.08

rel. d

efe

ct co

nce

ntr

atio

n

depth (nm)

exp. defect profile 1x1014

Ar/cm2

SRIM Argon profile

SRIM defect profile

Implantation damage in GaN

200 220 240 260 280 300 320 340 360 380 400

10

100

1000 aligned as-grown

aligned implanted

random

RB

S Y

ield

(coun

ts)

channel

RBS/C aligned spectra need correction

for dechannelling (in this case using the DICADA program, Gärtner

et al. NIMB 216 (1983) 275; 227 (2005) 522)

1x1014 Ar/cm2

∆𝜒𝑚𝑖𝑛=𝑌𝑎𝑠−𝑖𝑚𝑝𝑙𝑎𝑛𝑡𝑒𝑑𝑎𝑙𝑖𝑔𝑛𝑒𝑑

− 𝑌𝑎𝑠−𝑔𝑟𝑜𝑤𝑛𝑎𝑙𝑖𝑔𝑛𝑒𝑑

𝑌𝑟𝑎𝑛𝑑𝑜𝑚

Correction for

dechannelling

Page 25: Channelling Theory and Simulation Channelling Applications · 2015-07-20 · SPRITE Workshop 1 Channelling Theory and Simulation • Channelling Applications • The FLUX Code Katharina

SPRITE Workshop 25

→ Homogeneous Eu distribution

with depth ~0.1at%

→ Excellent crystal quality

(Minimum yield <3%)

GaN:Eu grown by MOCVD at 1000ºC

400 500 600 7000

1000

2000

3000

40001000 1200 1400 1600 1800

random

fit

<0001> aligned

co

un

ts

channel

Eu

x10

Ga

energy (keV)

Lattice site location of Eu in GaN

Page 26: Channelling Theory and Simulation Channelling Applications · 2015-07-20 · SPRITE Workshop 1 Channelling Theory and Simulation • Channelling Applications • The FLUX Code Katharina

SPRITE Workshop 26

→ Eu incorporated to ~100% on Ga-sites

→ Eu displaced (0.2Å) for sample grown at 900ºC

→ Eu clusters

Lattice site location of Eu in GaN

0.0

0.2

0.4

0.6

0.8

1.0

1.2

-2 -1 0 1 20.0

0.2

0.4

0.6

0.8

1.0

-0.8 0.0 0.8

Eu

Eu sim

Ga

Ga sim

norm

aliz

ed y

ield

900ºC

<1011>

<0001>

angle [deg.]

1000ºC

616 618 620 622 624 626 628 630

1E-4

1E-3

0.01

0.1

PL inte

nsity (

arb

. units)

wavelength (nm)

1000 ºC

950ºC

900ºC

PL exc. 348 nm at low T

Lorenz et al. APL 97 (2010) 111911

Page 27: Channelling Theory and Simulation Channelling Applications · 2015-07-20 · SPRITE Workshop 1 Channelling Theory and Simulation • Channelling Applications • The FLUX Code Katharina

SPRITE Workshop 27

Group-III Nitride Nanostructures

2D

InGaN/GaN quantum wells (QW)

LED

1D

GaN nanowires (NW)

Nano-LEDs, sensors

0D

GaN quantum dots (QD)

2-3 nm

InGaN QW

Page 28: Channelling Theory and Simulation Channelling Applications · 2015-07-20 · SPRITE Workshop 1 Channelling Theory and Simulation • Channelling Applications • The FLUX Code Katharina

SPRITE Workshop 28

Problems when going to nano-scale

Limited depth resolution

in conventional RBS (~20nm)

Problems:

Besides thickness and composition

is the width of the peak dependent on

- Energy resolution

- Intermixing of layers

- Roughness

In case of ambiguities need of

complementary experimental

techniques (TEM, AFM...)

Grazing incidence

400 450 500 550 600 650 7000

500

1000

1500

2000

25001200 1400 1600 1800

Ga

In random

fit

<0001> aligned

simulation

10nm layer

min

(In)=0.06

cou

nts

channel

Al

energy [keV]

AlInN/GaN

Page 29: Channelling Theory and Simulation Channelling Applications · 2015-07-20 · SPRITE Workshop 1 Channelling Theory and Simulation • Channelling Applications • The FLUX Code Katharina

SPRITE Workshop 29

GaN QD / AlN Multilayers

Chamard et al. Phys. Rev. B 69 (2004) 125327

150 b

ilay

ers

SiC

AlN (10nm)

AlN spacer: ~8 nm

GaN QD: 6ML

Grown by MBE using the

Stranski-Krastanow growth mode

Page 30: Channelling Theory and Simulation Channelling Applications · 2015-07-20 · SPRITE Workshop 1 Channelling Theory and Simulation • Channelling Applications • The FLUX Code Katharina

SPRITE Workshop 30

RBS Normal Incidence

Random and <0001> aligned Scan across <0001>

Excellent crystalline quality along c-axis min=4%!

100 200 300 400 500 6000

200

400

600

800

1000

1200

Al

co

un

ts

channel

<0001>aligned

random

Ga

-2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.00.0

0.2

0.4

0.6

0.8

1.0

Ga

Al

No

rma

lize

d Y

ield

Angle

<0001>

Page 31: Channelling Theory and Simulation Channelling Applications · 2015-07-20 · SPRITE Workshop 1 Channelling Theory and Simulation • Channelling Applications • The FLUX Code Katharina

SPRITE Workshop 31

Crystal Quality of QDs

450 500 550 600 6500

100

200

300

400

random

<0001> aligned86%

17%14%13%11%11%

co

un

ts

channel

7 GaN QD planes

min 12%

Crystal quality of each QD plane can be assessed

and does not change with depth

QD at surface show reduced channelling

probably due to strain relaxation and oxidation

7 Q

D p

lanes

SiC

AlN (10nm)

AlN spacer: ~40 nm

GaN QD: 3.5ML

200nm

Page 32: Channelling Theory and Simulation Channelling Applications · 2015-07-20 · SPRITE Workshop 1 Channelling Theory and Simulation • Channelling Applications • The FLUX Code Katharina

SPRITE Workshop 32

Buried SQW / SQD-plane

SiC

GaN SQW

AlN

AlN

10 nm

3.5 ML

26 nm

AlN

AlN

SiC

10 nm

3.5 ML

26 nm

GaN QD 100 200 300

0

300

600

900 =65º

=80º

=5º

cou

nts

channel

RBS XRR

AlN cap QD 8.9 (1.0) nm 9.4 nm

QD 2.6 nm (Vf=27%) 0.46 nm

AlN cap SQW 8.1(1.0) nm 8.8 nm

SQW 0.6 (1) nm 0.54 nm

Ga

Al

Page 33: Channelling Theory and Simulation Channelling Applications · 2015-07-20 · SPRITE Workshop 1 Channelling Theory and Simulation • Channelling Applications • The FLUX Code Katharina

SPRITE Workshop 33

Quality Buried SQW / SQD-plane

SQW QD-plane

-2.5 -2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.50.0

0.2

0.4

0.6

0.8

1.0

Ga SQW

Al cap

Al buffer

angle (deg.)

no

rmaliz

ed y

ield

-2.5 -2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.50.0

0.2

0.4

0.6

0.8

1.0

Ga QD

Al cap

Al buffer

angle (deg.)no

rmaliz

ed y

ield

<0001>

Crystal quality better in QD than in QW

Formation of misfit defects?

- misfit (GaN-AlN 2.5%) can lead to fomation of dislocations and stacking faults

as evidenced by TEM analysis (Kandaswamy et al. JAP 106 (2009) 013526)

min=15% min=5%

Page 34: Channelling Theory and Simulation Channelling Applications · 2015-07-20 · SPRITE Workshop 1 Channelling Theory and Simulation • Channelling Applications • The FLUX Code Katharina

SPRITE Workshop 34

Strain measurement: thin film

30.5 31.0 31.5 32.0 32.5 33.0 33.50.0

0.2

0.4

0.6

0.8

1.0 <2113>

31.7º

Ga

In

no

rmaliz

ed y

ield

angle (deg.)

32.4ºR

sapphire

GaN (1000 nm)

Al1-xInxN

cossin

Lorenz et al. PRL 97 (2006) 85501; JCG 310 (2008) 4058

Page 35: Channelling Theory and Simulation Channelling Applications · 2015-07-20 · SPRITE Workshop 1 Channelling Theory and Simulation • Channelling Applications • The FLUX Code Katharina

SPRITE Workshop 35

Problems when going to nano-scale

For example a buried GaN single quantum well (SQW) in AlN

-2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.00.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

Al

Ga

angle (deg.)

no

rma

lize

d y

ield

<-2113>

SiC

GaN SQW

AlN

AlN

10 nm

3.5 ML

26 nm

The GaN SQW is too thin to exhibit channelling effects on the beam

Ga-atoms act like an impurity

Scans do not shift but show asymmetries and flux peaking

Page 36: Channelling Theory and Simulation Channelling Applications · 2015-07-20 · SPRITE Workshop 1 Channelling Theory and Simulation • Channelling Applications • The FLUX Code Katharina

SPRITE Workshop 36

-1.5 -1.0 -0.5 0.0 0.5 1.0 1.5

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

2.2

Experiment

Simulation

no

rma

lize

d y

ield

angle (deg.)

Strain in Buried SQW / SQD-plane

-1.5 -1.0 -0.5 0.0 0.5 1.0 1.5

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6 Experiment

Simulation

no

rma

lize

d y

ield

angle (deg.)

SQW QD-plane

0.9 nm QD =0.12º T= -3.1%

1.7 nm QD =0.7º T= -1.6%

2.6 nm QD =0.5º T= -0.4%

0.9 nm QW =0.14º T=-3.9%

0.6 nm QW =0.22º T= -7%

QD partly relaxed but error in current

data anlysis is extremely high

MC simulations need to include sample imperfections and QD

T (fully strained)=-3.6% T (Raman, XRD)= -2.4% (Cros et al. PRB 76 (2007) 165403)

Page 37: Channelling Theory and Simulation Channelling Applications · 2015-07-20 · SPRITE Workshop 1 Channelling Theory and Simulation • Channelling Applications • The FLUX Code Katharina

SPRITE Workshop 37

High resolution RBS or MEIS

Electrostatic

analyzer

Position sensitive

detector

RBS HR-RBS / MEIS

Energy ~ 1-5 MeV (a, p) ~ 50-500 keV (a, p)

Detector system Si surface barrier detector Electrostatic analyser or magnetic spectrometer:

Resolution of detector system ~ 15 keV < 1 keV

Depth resolution ~10 nm < 1 nm

Probing depth ~1 mm ~20 nm

MEIS

Page 38: Channelling Theory and Simulation Channelling Applications · 2015-07-20 · SPRITE Workshop 1 Channelling Theory and Simulation • Channelling Applications • The FLUX Code Katharina

SPRITE Workshop 38

MEIS: Strain distribution in GaN QDs

Blocking

QD relax towards

the top of the pyramid

Jalabert et al. PRB 72 (2005) 115301

Relaxed c/a

QDs top

Page 39: Channelling Theory and Simulation Channelling Applications · 2015-07-20 · SPRITE Workshop 1 Channelling Theory and Simulation • Channelling Applications • The FLUX Code Katharina

SPRITE Workshop 39

RBS/C on nanowires?

- Vertically aligned NW grown by MBE on 111 Si

Page 40: Channelling Theory and Simulation Channelling Applications · 2015-07-20 · SPRITE Workshop 1 Channelling Theory and Simulation • Channelling Applications • The FLUX Code Katharina

SPRITE Workshop 40

Alignment of Nanowires

-2 -1 0 1 20.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1.1

1.2

1.3

-2 -1 0 1 2

norm

aliz

ed y

ield

<0001>

Si

Ga

<-2113>

angle [deg.]

-2 -1 0 1 2

<10-11>

- Preferential orientation of

nanowires:

[111] Si || [0001] GaN

[11-2] Si || [10-10] GaN

Si

Ga/N

250 300 350 400 450 500 550 600 6500

500

1000

1500

2000

random

aligned

cou

nts

channel

GaN NW

Si

Page 41: Channelling Theory and Simulation Channelling Applications · 2015-07-20 · SPRITE Workshop 1 Channelling Theory and Simulation • Channelling Applications • The FLUX Code Katharina

SPRITE Workshop 41

Mosaicity of Nanowires

-1 0 10.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1.1

1.2

1.3

1.4

-1 0 1

no

rma

lize

d y

ield

<0001>

to plane

<2113>

to plane

angle [deg.]

-1 0 1

data

0.4º tilt

0.3º tilt

0.5º tilt

data

0.5º twist

0.4º twist

0.6º twist

<2113>

to plane

Ion channelling in NWs

allows determination of

orientation, tilt and twist

via Monte Carlo

simulations:

- Tilt: 0.4º

- Twist: 0.5º

Page 42: Channelling Theory and Simulation Channelling Applications · 2015-07-20 · SPRITE Workshop 1 Channelling Theory and Simulation • Channelling Applications • The FLUX Code Katharina

SPRITE Workshop 42

Implantation damage in GaN

Eu implantation 300 keV at RT

Sigmoidal shaped damage build-up curve

Efficient dynamic annealing

0.1 1 100.0

0.2

0.4

0.6

0.8

1.0

IV

IIIregime I

ma

x.

de

fect le

ve

l

fluence (1015

at/cm2)

bulk peak

surface peak

II

Lorenz et al. J. Phys. D

42 (2009) 165103

Page 43: Channelling Theory and Simulation Channelling Applications · 2015-07-20 · SPRITE Workshop 1 Channelling Theory and Simulation • Channelling Applications • The FLUX Code Katharina

SPRITE Workshop 43

Implantation damage in GaN

0.1 1 100.0

0.2

0.4

0.6

0.8

1.0

IV

IIIregime I

max. defe

ct le

vel

fluence (1015

at/cm2)

bulk peak

surface peak

II

HRTEM

TEM

0002

dark field

- Point defect clusters

- Low concentration of stacking faults

Page 44: Channelling Theory and Simulation Channelling Applications · 2015-07-20 · SPRITE Workshop 1 Channelling Theory and Simulation • Channelling Applications • The FLUX Code Katharina

SPRITE Workshop 44

Implantation damage in GaN

0.1 1 100.0

0.2

0.4

0.6

0.8

1.0

IV

IIIregime I

max. defe

ct le

vel

fluence (1015

at/cm2)

bulk peak

surface peak

IIHRTEM

- Increasing number of stacking faults

Page 45: Channelling Theory and Simulation Channelling Applications · 2015-07-20 · SPRITE Workshop 1 Channelling Theory and Simulation • Channelling Applications • The FLUX Code Katharina

SPRITE Workshop 45

Implantation damage in GaN

0.1 1 100.0

0.2

0.4

0.6

0.8

1.0

IV

IIIregime I

max. defe

ct le

vel

fluence (1015

at/cm2)

bulk peak

surface peak

II

- Nanocrystalline surface layer with voids

- Stacking fault density in bulk saturates

0 20 40 60 80 100 120 1400.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

defect distribution

Eu-profile at-%

rel. c

on

c. p

oin

t d

efe

cts

Eu

co

nc

en

tra

tio

n (

at-

%)

depth (nm)

Page 46: Channelling Theory and Simulation Channelling Applications · 2015-07-20 · SPRITE Workshop 1 Channelling Theory and Simulation • Channelling Applications • The FLUX Code Katharina

SPRITE Workshop 46

InxGa1-xN/GaN: Thin film

200 250 300 350 400 450 500 550 600 650 7000

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

5500 experimental data

fit

co

un

ts

channel

In

Ga

N

Fit results:

50 nm In15.9Ga84.1N sapphire

GaN (1-6 mm)

InxGa1-xN

A fit (e.g. using the NDF code) gives the thickness and composition of the film

and can give information on compositional gradients, roughness, contaminations

etc.

Page 47: Channelling Theory and Simulation Channelling Applications · 2015-07-20 · SPRITE Workshop 1 Channelling Theory and Simulation • Channelling Applications • The FLUX Code Katharina

SPRITE Workshop 47

InxGa1-xN/GaN: Manual Analysis

200 250 300 350 400 450 500 550 600 650 7000

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

5500 experimental data

fit

co

un

ts

channel

In

Ga

N

16.0

)1(1

191.0/221996.62550

/482264.21220

)(

)(

Ga

In

Ga

In

Ga

In

rGa

rIn

Ga

In

iri

N

N

N

N

xx

x

N

N

strbarn

strbarn

InY

GaY

N

N

NY

Fit results:

50 nm In0.159Ga0.841N

2550 cnts

1220 cnts

2

cm

atN

i

Composition from fit and manual analysis match perfectly

sapphire

GaN (1-6 mm)

InxGa1-xN

Page 48: Channelling Theory and Simulation Channelling Applications · 2015-07-20 · SPRITE Workshop 1 Channelling Theory and Simulation • Channelling Applications • The FLUX Code Katharina

SPRITE Workshop 48

200 250 300 350 400 450 500 550 600 650 7000

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

5500 experimental data

fit (50 nm)

simulation 10nm

thicknessco

un

ts

channel

In

Ga

N

InxGa1-xN/GaN: Going to Nanoscale

For very thin layers the height of the In-peak depends not only on composition

but also on the thickness of the layer due to the limited depth resolution.

sapphire

GaN (1-6 mm)

InxGa1-xN

x=0.16

Page 49: Channelling Theory and Simulation Channelling Applications · 2015-07-20 · SPRITE Workshop 1 Channelling Theory and Simulation • Channelling Applications • The FLUX Code Katharina

SPRITE Workshop 49

InxGa1-xN/GaN: Multi Quantum Well (MQW)

QW thickness and QW composition difficult to measure with most techniques

- XRD measured the period and average composition

- PIXE, WDX measures the total In-content; QW thickness needs to be known

- SIMS suffers from artefacts due to contaminations from the sides

- TEM+EDX possible but very time consuming

5 samples with different InN content

InxGa1-xN/GaN MQW

5 periods

Nominal QW thickness 3nm

Grown by Metal Organic Chemical

Vapour Deposition (MOCVD) sapphire

GaN (1-6 mm)

sapphire

GaN (1-6 mm)

InGaN 3 nm

GaN 21 nm

Page 50: Channelling Theory and Simulation Channelling Applications · 2015-07-20 · SPRITE Workshop 1 Channelling Theory and Simulation • Channelling Applications • The FLUX Code Katharina

SPRITE Workshop 50

InxGa1-xN/GaN: Multi Quantum Well (MQW)

Composition and thickness cannot be determined unambiguously

(complementary measurements necessary e.g. TEM).

Period, total InN content and “product” thickness × composition.

Assuming the nominal thickness of 3 nm, x was determined to vary from 2 to 14 %

350 400 450 500 550 600 650 7000

200

400

600

800

1000

1200

1400

1600

1800

2000

2200

=60º=70º

=5º

cou

nts

channel

=40º

RPI198A fit using ~5nm QW

350 400 450 500 550 600 650 7000

200

400

600

800

1000

1200

1400

1600

1800

2000

=60º

=70º

=5º

cou

nts

channel

=40º

RPI198A fit using ~3nm QWFit using ~3nm QW, x=0.11 Fit using ~5nm QW, x=0.07

sapphire

GaN

(1-6

mm

)

sapphire

GaN

(1-6

mm

)

Page 51: Channelling Theory and Simulation Channelling Applications · 2015-07-20 · SPRITE Workshop 1 Channelling Theory and Simulation • Channelling Applications • The FLUX Code Katharina

SPRITE Workshop 51

Crystal Quality in QWs

300 400 5000

500

1000

1500

2000

2500

3000

3500

4000

4500

460 480 500 520 5400

100

200

300

400

500

co

un

ts

channel

RPI198A

Ga

In

random

aligned

channel

four QW

min

=4%

Minimum yield for Ga: < 2% in all samples

Minimum yield for In: 2-10% (better for thinner GaN barrier layers)

Page 52: Channelling Theory and Simulation Channelling Applications · 2015-07-20 · SPRITE Workshop 1 Channelling Theory and Simulation • Channelling Applications • The FLUX Code Katharina

SPRITE Workshop 52

Grazing Incidence

Layer Material Thickness

[nm]

1 GaN/AlN 3.435

2 AlN 4.558

3 GaN/AlN 2.669

4 AlN 5.202

5 GaN/AlN 2.642

6 AlN 5.082

7 GaN/AlN 2.557

8 AlN 5.037

9 GaN/AlN 2.663

160 180 200 220 240 260 2800

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

5500

Fit

Experimental Data

channel

cou

nts

GaAlTilt 86º

Input:

Cylindrical QD: Height 2.6 nm

Radius 8.5 nm

QD volume fraction 40%

Page 53: Channelling Theory and Simulation Channelling Applications · 2015-07-20 · SPRITE Workshop 1 Channelling Theory and Simulation • Channelling Applications • The FLUX Code Katharina

SPRITE Workshop 53

Simulating QD with NDF

1N. Barradas et al. APL 71 (1997) 291. 2J.P. Stoquert et al. Phys. Rev. B 66 (2002) 144108. 3N. Barradas et al. unpublished

- NDF1 (IBA Data Furnace) spherical2 and cylindrical3 QD

→ cylindrical QD: Height 2.6 nm

Radius 8.5 nm

NDF calculates:

- Quantity of material crossed

- Energy spread due to

difference in stopping power

→ volume fraction

Page 54: Channelling Theory and Simulation Channelling Applications · 2015-07-20 · SPRITE Workshop 1 Channelling Theory and Simulation • Channelling Applications • The FLUX Code Katharina

SPRITE Workshop 54

Volume fraction of GaN QD

Volume-fraction of GaN QD: 0.4

Good agreement with TEM

Uncovered QDs at surface are bigger

(confirmed by TEM, Gogneau et al. JAP 96 (2004) 1104)

220 240 260 2800

1000

2000

3000

4000

V = 0.30

V = 0.40

V = 0.45

Experimental Data

channel

co

un

ts

GaTilt 86º