Using a three head Laytec detector system on a 6x2 Thomas Swan ...

<strong>Using</strong> a <strong>three</strong> <strong>head</strong> <strong>Laytec</strong> <strong>detector</strong> <strong>system</strong> on 

a 6x2 Thomas Swan MOCVD reactor 

A.J.SpringThorpe and W. Benyon 

National Research Council of Canada 

Institute for Microstructural Sciences 

Canadian Photonics Fabrication Centre 

1200 Montreal Rd., Ottawa.Ontario 

Canada [K1A 0R6]

CPFC 

6x2 [7x2] T/S MOCVD reactor 

�Mainly 3x3 and 1x4 configuration 

�For InP and GaAs based alloys 

�Quartz diffuser plate 

�Exhaust pipe-line “Widget” 

�<strong>Laytec</strong> ‘in-situ’ monitoring 

�Pyrometry @ 950nm 

�reflectance @ 633nm [GaAs] and 950nm [InP] 

A.J.SpringThorpe – <strong>Laytec</strong> seminar - Metz – June 2008 

2

InP-based materials 

�1.3 and 1.55μm lasers 

� FP, DFB and BH 

�InGaAsP, InGaAs and InAlGaAs 

�P-i-N <strong>detector</strong>s - InGaAs 

�APD’s, QWIP’s 

�HBT’s 

�Quantum Dots 


3

GaAs, GaInAs, GaInP and AlGaAs 

�980nm lasers 

�Waveguides 

�Bragg reflectors 

�Multi-junction Solar Cells 

�QWIP’s - QCL’s 

�Quantum Dots 

�2DEG’s 


4

Single <strong>Laytec</strong> reflectance <strong>head</strong> 


5

<strong>Laytec</strong> optical monitoring <strong>head</strong> placement on the MOCVD reactor 


6

<strong>Laytec</strong> <strong>detector</strong> <strong>head</strong> layout 

DTT 1: 633 nm 

950 ± 70 nm DTT 2: 633 nm 

950 ± 70 nm 

950 ± 10 nm 

DTT 3: 950 ± 

70 nm 

A 

B 

C 

D 

D Ξ 


B 

C sees the susceptor 

7

GaAs and AlAs calibration 

Mirror 

White light 

AsH 3 

Detectors 

@633nm 

@950nm 

GaAs substrate 

TMG 

TMA 

TMA-1 TMG-1 TMA-2 TMG-2 


8

InP growth rate calibration @ ~650 o C 

4.758Å/s 

4.625Å/s 

4.758Å/s 

+2.9% 

-1.8% 

Relative reflectance 

0.380 

0.360 

0.340 

0.320 

0.300 

0.280 

Relative reflectance @ 950nm 

Detector 1 

Detector 2 

Detector 3 

0.260 

1500 2000 2500 3000 3500 4000 4500 

time/s 

Special 3x3 susceptor to use all <strong>three</strong> <strong>detector</strong>s 


9

Reflectance at 950nm during n-InP epitaxy 

Substrate 

1.3E18 S-InP 

5E18 Si-InP 

5E17 Si-InP 


10

MOCVD Quantum dots 

�InAs 

�50%InGaAs 

�Need ‘in-situ’ monitoring 


11

Formation of InAs QDs – RHEED signature 

T=0s, 

0ML InAs 

GaAs c(4x4) 

T=1s, 

0.08ML InAs 

T=QD-0.5s, 

T=QD 0.5s, 

1.86ML InAs 

T=QD+0.5s, 

1.94ML InAs 

T=QD+2.0s, 

2.06ML InAs 

T=QD+4s, 

2.21ML InAs 

With thanks to Dr.Z. Wasilewski of NRC/IMS Epitaxy 


12


13

TMI bubbler configuration 

Carrier 

gas in 

0-1000 sccm 

Pusher 

Massflow controllers 

Flow in 

0-1000 sccm 

Minimum flow ~50 sccm 

Ξ ~0.1mL/s 

x 

x x 

To exhaust 

Pressure 

controller 

Control 

valves 

Organometallic 

Bubbler 

To 

reactor 


14

Minimum InAs growth rate calibration 

RADS:- 

5x 15sec TMI @ ~50sccm 

200sec TEG @ 190sccm 

T g ~ 500 o C 

GaAs – 353.9 Å – 1.77Å/s 

InAs – 3.81Å - ~0.254Å/s - ~0.083mL/s 

22sec ~ 1.84mL 


15

Estimation of InAs critical deposition thickness 

Relative reflectance 

1.014 

1.012 

1.010 

1.008 

1.006 

1.004 

1.002 

1.000 

SI-GaAs - 0deg 

SI-GaAs - 2deg 

Critical 

deposition 

thickness 

~2+-0.22mL 

0 50 100 150 200 250 300 

Growth time [seconds] 


16

Estimation of 50%InGaAs critical deposition thickness 

5.0 5.2 5.4 5.6 5.8 6.0 6.2 6.4 6.6 6.8 7.0 mL 

Relaxation starts after ~5.8mL 


17

Comparison between 633nm and 950nm reflectance 

633nm 950nm 

5.0 5.2 5.4 5.6 5.8 6.0 6.2 6.4 6.6 6.8 7.0 mL 5.0 5.2 5.4 5.6 5.8 6.0 6.2 6.4 6.6 6.8 7.0 mL 

δR~1.2% δR~0.8% 

Reflectance changes are ~50% larger at 633nm as compared to 950nm 


18

Surface dot growth test – 

Structure 

22 sec InAs 

Reflectance at 633nm 

Cooldown 

AFM scan 


19

Buried dot growth test – 

Structure 

Photoluminesce 

532nm – 11mW 

22 sec InAs 


GaAs 

Surfscan 

10μm defects 

Plan View TEM 

500nm 


20

Structure 

Indium-Flush to improve surface morphology - 2 

25 sec InAs ~2mL 

10nm GaAs 

Ramp to 620C 

25nm GaAs 

60 sec anneal 

Surfscan 


10nm GaAs 

25nm GaAs 

Plan View TEM 

500nm 

~1.5E9 dots/cm 2 

~22nm in size 


21

Reflectance @ 633nm 

1.025 

1.020 

1.015 

1.010 

1.005 

1.000 

0.995 

0.990 

M1163 Reflectance @ 633nm 

Temperature (C) 


640 

620 

600 

580 

560 

540 

0.985 

520 

0 50 100 150 200 250 300 

Time (seconds) 

500nm 

2.5mL InAs 

Increased InAs deposition 

Temperature ( o C) 

InAs ~2.5 and 3.0mL 

10nm GaAs 

Ramp to 620C 

25nm GaAs 

60 sec anneal 

1.025 

1.020 

1.015 

1.010 

1.005 

1.000 

0.995 

0.990 

~1.8E10/cm 2 ~3.2E10/cm 2 


3.0mL InAs 

M1162 Reflectance @ 633nm 


0.985 

520 

0 50 100 150 200 250 300 

Time (seconds) 

Temperature(oC) 

500nm 


640 

620 

600 

580 

560 

540 

22 

Temperature ( o C)

50% InGaAs surface QD’s on vicinal substrates – AFM 1μm square 

0-deg - 6.6E10/cm2 2-deg – 8.4E10/cm2 5-deg – 9.6E10/cm2 10-deg – 1E11/cm2 

1075 

0.00 2.00 4.00 6.00 8.00 10.00 


PL wavelength [nm] 

1275 

1250 

1225 

1200 

1175 

1150 

1125 

1100 

10 deg 

Arsine [sccm] 

0 Deg 

2 Deg 

5 Deg 

23

Conclusions:- 

�The <strong>three</strong> <strong>head</strong> reflectance unit enables precise growth rate 

and temperature uniformity measurements 

�Simple reflectance measurements can be used to 

monitor the onset of relaxation in quantum dot deposition 

�Shorter wavelengths are better – ~1.3% δR @ 633nm 


24

Acknowledgements:- 

�For TEM analysis 

Dr. Xiaohua Wu – NRC/IMS* 

Mr.Guy Parent – NRC/IMS 

�For AFM analysis 

Ms.Simona Moisa – NRC/IMS 

�For financial support 

Canadian Photonics Fabrication Centre 

CMC Micro<strong>system</strong>s 

*National Research Council of Canada/Institute for Microstructural Sciences 


25

Using a three head Laytec detector system on a 6x2 Thomas Swan ...

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