Preparation of semiconductor nanomaterials

Studijní program: Nanotechnologie Studijní obor: Nanomateriály (organizuje prof. J. Šedlbauer, FPP TU v Liberci)

Preparation of semiconductor nanomaterials 2013/2014 (prof. E. Hulicius, FZÚ AV ČR, v.v.i.,)

Nanocon 1, Rožnov, 2009

Nanostruktury pro optoelektroniku – souboj kaskádových laserů a struktur typu W o reálnou aplikaci jako zdroj laserového záření v blízké infračervené oblasti Eduard Hulicius Fyzikální ústav AV ČR, v. v. i.

Abstrakt V přednášce budou stručně popsány struktury kaskádových polovodičových laserů a laserové W struktury druhého typu na bázi GaSb. Dále budou diskutovány principy činnosti těchto struktur a budou srovnány s klasickými hetero- a nanostrukturami. Bude objasněn efekt „nano“, pomocí kterého se překonává omezení klasických struktur způsobené nezářivými Augerovými rekombinacemi. Bude zmíněn aplikační potenciál uvedených součástek jako koherentních i nekoherentních zdrojů záření v blízké infračervené oblasti a také současná situace ve vývoji a na trhu. Budou využity a prezentovány zkušenosti autora z EU projektů ADMIRAL, GLADIS a NEMIS – co se týká struktur typu W a z návštěv řady zahraničních pracovišť, kde se připravují a studují kaskádové lasery.

Definice spektrálních oblastí: (Tab 1.1.). Vztahy mezi uvedenými veličinami vlnovou délkou , energií E, frekvencí f a vlnočtem : m 1.24/E (eV), f (THz) = 300 / m (cm-1) = 10 000/ m Visible

Near Infrared (NIR)

Mid Infrared (MIR)

Far Infrared mm (FIR or Wave THz)

Wavelength (m)

0.4-0.7

0.7-2.0

2.0-20

20-1000

>1000

Energy (eV)

1.7-3.1

0.6-1.7

0.06-0.6

0.001-0.06

<0.001

Frequency (THz)

400-750

150-400

15-150

0.3-15

<0.3

500-5000

10-500

<10

Wavenumber 14000-25000 5000-14000 (cm -1)

Spektrální oblasti a aplikace LD Hlavní proud –:

viditelná a blízká infračervená oblast

Jsou to materiály dnes většinou dobře zvládnuté – z důvodů historických i technologických. Stále zůstává prostor na zlepšování parametrů, i zavádění nových struktur (kvantové tečky), převratný „break through“ ale neočekávám. Přiléhající oblasti jsou ultrafialová (nitridy, ZnO, diamant, ...? – větší hustota optických pamětí, medicínské aplikace, ..) střední infračervená:

Střední infračervená oblast elektromagnetického záření, která se obvykle definuje od 2 do 20 μm, je pro optoelektroniku velmi zajímavá nejen z hlediska aplikací: •Detekce, přesné a citlivé měření koncentrací různých látek (hlavně atmosférických polutantů, ale i různých průmyslových plynů) laserovou absorpční spektroskopií; •v lékařství - diagnostika - složení dechu, • i terapie - aktivace léků IČ zářením, které pronikne dost hluboko; •"free space" komunikace (atmosférické okno); •konverze optické energie na elektrickou (termofotovoltaika); •ve vojenství – atmosférické okno pro laserové zbraně; detektory, citlivá termovize; detekce výbušnin, jedů a pod.; ostraha v 2. IČ oblasti ------------------Historicky první aplikačně zaměřené práce zdrojích v (blízké) MIR oblasti byly podníceny pracemi na fluoridových vláknech s ještě nižším absolutním útlumem než mají křemenná vlákna (vlákna – Dianov, FIAN; lasery - FIAN, GIREDMET,…)

Wavelength Modulation Spectroscopy (WMS)

Závislost šířky zakázaného pásu na mřížkové konstantě vybraných polovodičových materiálů

Střední infračervená oblast je zajímavá i z hlediska nejmodernějšího materiálového inženýrství a nanotechnologií vzhledem k využití kvantových jevů v nových součástkách: •"W" struktury heteropřechodů II. typu - omezení nežádoucí Augerovy rekombinace; •kaskádové lasery – patrně současné nejsložitější polovodičové součástky; vlnová délka se mění geometrií, architekturou struktury •negativní luminiscence – pozoruhodný jev s zajímavými aplikacemi;

LD Laser Diode Laserová dioda

Rekombinace a propustné napětí

Emisní spektrum LED

?

Spontánní a stimulovaná emise LD

Zisk a ztráty v závislosti na energii fotonů, pro různé koncentrace elektronů v aktivní oblasti.

Laserování začíná na dlouhovlnné straně spektra (absorpce).

hustoty stavů

Appendix 1 Augerova nezářivá rekombinace

Dvoustupňový proces Augerovy nezářivé rekombinace. V této jednoduché pásové struktuře musí být přechody šikmé (zachování hybnosti k) (CHCC)

Energie z rekombinace je využita pro přechod mezi těžkými a lehkými děrami (CHHL)

Obvyklý případ pro AIIIBV polovodiče je excitována díra ze spinorbitálně odštěpeného pásu (CHHS)

Rezonanční Augerův proces v křemíku vyžaduje účast dvou elektronů (typ CHCC)

Naše výsledky v oboru struktur pro polovodičové lasery W-DHS (Double HetroStructure)

Podobně jako u LED je viditelná a blízká IČ oblast převážně průmyslová záležitost. Příprava LD pro střední a vzdálenou IČ i ultrafialovou oblast je velkou výzvou pro badatele. Často je také důležité nahradit stávající typy LD novými s výrazně lepšími parametry.

Kvantové jámy (QW) Heteropřechody druhého typu Struktury s napnutými vrstvami Kvantové tečky (QD)

AlGaAs-n typ 570 nm GaAs: buffer 230 nm

GaAs:Te substrate

AlGaAs 400 nm

GaAs 150 nm

AlGaAs 320 nm

SPSLS 12x (InAs / GaAs)

AlGaAs-p typ 570 nm GaAs 700 nm

Srovnání laserů s ternární a „supermřížkovou“ (MQW) aktivní oblastí InAs/GaAs laser se supermřížkou

Ternární InGaAs QW laser

120

200

Iex=2 A Iex=2.25 A Iex=2.5 A Iex=3 A T=300 K

0.4

Optical Power [W]

Intensity

Optical Power [a.u.]

100

EL

0.6

0.2 0.0 1.1

1.2 1.3 Emission Energy [eV]

1.4

100 laser A o 25 C o 40 C o 50 C o 60 C o 70 C o 80 C o 85 C

50

0 0

1000

2000

Intensity

0.8

0.8

150

1.0

T0 = 109 K

1.0

3000

4000 2

Current Density [A/cm ]

5000

80

PL EL Iex=0.46A T=300K

0.6 0.4

T0 = 126 K

0.2 0.0

1.1

60

1.2 1.3 Emission Energy [eV]

1.4

laser B 25°C 35°C 45°C 55°C 65°C 75°C 85°C

40

20

0

6000

0

100

200

300

400 2

Current Density [A/cm ]

500

600

Podobně jako u LED je viditelná a blízká IČ oblast převážně průmyslová záležitost. Příprava LD pro střední a vzdálenou IČ i ultrafialovou oblast je velkou výzvou pro badatele. Často je také důležité nahradit stávající typy LD novými s výrazně lepšími parametry. Kvantové jámy (QW)

Heteropřechody druhého typu Struktury s napnutými vrstvami Kvantové tečky (QD)

Základní způsoby generace záření ve (střední) infračervené oblasti

EU projekty, týkající se MID IR oblasti Control of Enviromental Pollution by Tunable Diode Laser Absorption Spectroscopy in the Spectral Range 2 - 4 µm ERB 3512 PL 940813 * (COP 813) (1994 - 1997) Actaris SAS, DE, Schlumberger Industries SA, FR, University of Montpellier, FR, Thales, FR, Nanoplus, DE, Gaz de France, FR, , Gas Natural, ES, Omnisens, CH

Advanced Room Temperature Mid-infrared Antimony-based Lasers by MOVPE – (ADMIRAL) ERB INCO COPERNICUS 20CT97*BRITE/EURAM III-BRPR-CT97-0466 (1997-2000) EPICHEM, Bramborough, UK, AIXTRON, Aachen, Germany, RWTH, Aachen, Germany, UM2 University of Montpellier, France

Gas Laser Analysis by Infra-red Spectroscopy – (GLADIS) IST-2001-35178 (2002 - 2005) UM2 University of Montpellier, France, Ioffe Physicotechnical Institute St. Petersburg, Russia, Fraunhofer Institute, Garmisch-Partenkirchen, Germany, Institute of Electron Technology, Warsaw, Poland, IBSG, St. Petersburg, Russia

Optical Power [a.u.]

1400

25°C 50°C

1200 1000 800 600 400 200 0

0

10

20

30

40

Excitation Current [mA]

0 -10

EL Intensity [dB]

-20

T=25°C T=50°C T=70°C Iex=70 mA

-30 -40 -50 -60 -70 -80 -90

2340

2360

2380

2400

2420

2440

Wavelength [nm]

2460

2480

50

The NEMIS project aims at the development and realisation of compact and packaged vertical-cavity surface-emitting semiconductor laser diodes (VCSEL) for the 2-3.5 µm wavelength range and to demonstrate a pilot photonic sensing system for trace gas analysis using these new sources. The availability of electrically pumped VCSELs with their low-cost potential in this wavelength range that operate continuously at or at least near room-temperature and emit in a single transverse and longitudinal mode (i. e. single-frequency lasers) is considered a basic breakthrough for laser-based optical sensing applications. These devices are also modehop-free tuneable over a couple of nanometers via the laser current or the heatsink temperature. They are therefore ideal and unmatched sources for the spectroscopic analysis of gases and the detection of many environmentally important and/or toxic trace-gases, which is a market in the order of 10 million Euro today with an expected increase into several 100 million Euro with the availability of the new VCSELs

Outline  Application: trace gas sensing  BTJ-VCSEL Design  BTJ-VCSEL Results  Summary  Outlook

NEMIS project NEMIS – IST 2005 31845 : New Mid-Infrared sources for photonic Sensors (University Montpellier 2 (F), WSI (G), IOP (Cz), Chalmers (Sw), Vertilas (G), Omnisens (CH), Siemens (G))

Gas analysis by absorption spectroscopy in the Mid-IR for environmental monitoring, industrial process control, … (CH4 and NH3 detection at 2.3 µm, HF at 2.5 µm, …) Single frequency, P > 1 mW, CW, RT lasers

VCSELs  EP GaSb-based VCSEL

NEMIS project :

 Three wavelength range of main interest defined by end users : 2.3 µm, 2.7 µm, 3.3 µm

Create new mid-infrared sources for photonics sensors

State of the art before NEMIS p-contact

1st monolithic µ-cavity GaSb-based EP-VCSEL :

P.I.N. structure : 2 AlAsSb/GaSb (N and P) DBRs, GaInSb/GaSb Type-II MQWs Laser operation at 2.2µm in pulsed regime (200 ns/1 KHz) at RT with Ith>2kA/cm2 (A. Baranov et al., Electronics Letters, 1998, Vol.34, p. 281)

p-DBR MQW Active region

n-DBR

GaSb n-substrate n-contact

2

Current Density (kA/cm )

1.0

p-doped n-doped

0.8

 Voltage drop per pair @ 1 kA/cm2 :

0.6

• Te-doped DBR ~ 25 mV/pair • Be-doped DBR ~ 155 mV/pair

0.4 0.2 0.0

 Optical losses :

Contact diameter: 200 µm

-0.2 -0.4

• Te-doped DBR ~ 5 – 10 cm-1 • Be-doped DBR > 40 cm-1

-0.6 -3

-2

-1

0

1

2

3

4

* Perona et al. Semi. Sc. Tech (22), 2007

Voltage (V)

PIN PIN structure structure no no optimized optimized for for RT RT CW CW operation operation

Buried Tunnel Junction p+

n+

GaSb:Si InAsSb:Si

n+ p+

e ne rgy

 = 2.5 × 10-6  cm2 with n = 1 × 1019 cm3

+

-

pos ition

Substitution: p-doped by n-doped material

 reduced electrical resistance  lower absorption losses

Buried Tunnel Junction p+ GaSb:Si

p+

e ne rgy

n n+ p+ space charge region pos ition

d blocking pn-junction

current confinement by diameter d

Summary  GaSb-based

VCSEL design with buried tunnel junction

 first device results: CO detection (57 ppm) → cw

laser emission up to 50°C @ ≈ 2.33 µm → single mode emission Outlook → reduction of absorption within the cavity → improvement of current confinement → better matching of field maximum and active region position  improvement

of device performance (output power and

efficiency) extending VCSEL emission wavelength to 2.5 - 3 µm

Základní způsoby generace záření ve (střední) infračervené oblasti

Tunable Emission Over a Wide Spectral Range

Conduction band schematic of GaInAs/ AlInAs quantum cascade laser lattice matched to InP.

Cross sectional schematic of laser waveguide structure.

Photograph of a self-contained prototype quantum cascade laser pointer realised at CQD.

Demonstrated single mode emission from quantum cascade lasers spanning both atmospheric windows.

Distributed Feedback (DFB) Quantum Cascade Lasers

High Performance Lasers Operating at Room Temperature 75 period waveguide core Cavity: 3 mm x 25 m

Cross section image of a buried-ridge QCL laser.

Cross section image of a Au electroplated QCL.

Electrical and optical characteristics of a typical 9 m quantum cascade laser operating in pulsed mode at room temperature. Peak output power of 2.5 W is the highest power for a quantum cascade laser in these conditions.

Highest average power QCL.

Comparison of groups >4 m

M. Razeghi, Center for Quantum Devices, Northwestern Univ., Evanston

Uncooled Infrared (5-12 m) Quantum Cascade Lasers Lasers operating in the mid- and far-infrared (5-12 m) spectral region are desirable for many applications. Up until recently, the only such laser technologies available were based on bulky gas or solid-state lasers as well as cryogenically cooled semiconductor lasers. One of the most exciting projects at the Center for Quantum Devices (CQD) is uncooled infrared quantum cascade lasers (QCLs), which, being a semiconductor laser, is inherently compact and will help eliminate the need for bulky and unreliable cryogenic cooling. This translates to a smaller, cheaper, system with a longer lifetime and less maintenance. Besides our current records with respect to threshold current density and high peak power, we have recently demonstrated the highest power continuous wave QCLs at room temperature.

Závěr (můj) W-DHS LD: ano 2 – 3,5 µm (možná do 4 µm) QCL: ano 200 – 3,5 µm (možná do 3 µm) Zatím

Děkuji za pozornost

Appendix 2

MBE technology for QCL and W-DHS

MBE ve FZÚ AV ČR, v. v. i.

Appendix 3

Project activity overview WP4 - Characterisation nd (2 year) Eduard Hulicius Institute of Physics, AS CR, Prague, Czech Republic

Contents • WP objectives • Progress towards objectives – – – –

Optical constant of GaSb:Te and AlAsSb used for DBR Noise measurement High resolution absorption spectra of selected gases Ageing equipment and measurement

• Deviations from plan • Deliverables/Milestones 50

WP objectives  Optical constant of GaSb:Te and AlAsSb  Noise measurement  High resolution absorption spectra of selected gases  Ageing measurement 51

Progress towards objectives Optical constant of GaSb:Te and AlAsSb

OK, interesting results, partly published, will be continued.

 Noise measurement First set was measured, the second is measured, publication is prepared (comparison of GLADIS-FP and NEMIS-VCSEL).

 High resolution absorption spectra of selected gases Till now service, will be continued with NEMIS lasers as planned.

 Ageing measurement First results are available (pulsed only), cw and more lasers and higher temperatures will be made during the third year (and after!) as planned. 52

Optical constants of GaSb:Te and AlAsSb Equipment used: FTIR reflectance at the angle of incidence of 10 deg, Bruker IFS55 and IFS66 (vacuum), room temperature; Evaporated and sputtered gold as reference. MIR ellipsometer attached to Bruker IFS55. NIR-VIS-UV reflectance at the angle of incidence of 10 deg, Varian Cary, room temperature. NIR-VIS-UV reflectance at the angle of incidence of 0 deg, Avantes AvaSpec-2048, room temperature. Silicon as reference. 53

Optical constants of GaSb:Te FIRrefl-FIRR1

1.0 18

2.5x10

REFLECTANCE

0.8

17

5x10

0.6 18

Nf = 4x10 cm

18

1x10

-3

0.4

0.2 17

0.0

-3

GaSb:Te (2 m, Nf) / GaSb:Te (Ns=2.5x10 cm )

0

200

400

600 -1

WAVENUMBER (cm )

Effect of Te doping on the optical response of GaSb:Te is best seen in the FIR spectra: plasma of free carriers overlap with the restrahlen band of the polar vibrations of the GaSb lattice (TO frequency of 226.6 cm-1). Both free carriers and phonon contribute to lowering of the refractive index in the MIR range. Oscillator strengths obtained from the Drude-Lorentz fit quantify the effect. At lower dopings (<= 1E18 cm-3), the spectra are sensitive to the film thickness. 54

Optical constants of GaSb:Te

GaSbFilms-ReflGap 17

-3

Wgap, bare substrate, 2.5x10 cm

REFLECTANCE

0.360

17

5x10

0.355

18

1x10

18

2.5x10 18

Nf = 4x10 cm

0.350

-3

17

-3

GaSb:Te (2 m, Nf) / GaSb:Te (Ns=2.5x10 cm )

5500

6000

6500

7000

-1

W (cm )

The bandgap range of GaSb:Te: Fermi energy penetrates the conduction band and increases the onset of absorption (Moss-Burstein shift). This slightly lowers the refractive index in MIR. 55

Optical constants of GaSb:Te MIRrefl-DerR2 18

Nf = 4x10 cm

-3

18

2.5x10

0.0002

17

bare substrate, 2.5x10 cm

18

1x10

Eg

17

5x10

dR/dW (cm)

-3

0.0000

-0.0002

17

-3

GaSb:Te (2 m, Nf) / GaSb:Te (Ns=2.5x10 cm )

2000

4000

6000

-1

W (cm )

The transparent range of intrinsic or slightly doped GaSb: The (thick) substrate is transparent and the spectra are influenced by the reflections on the (rough) backside; this is significant, since the optical contrast between the substrate and epilayer is small and the patterns produced by the coherent interference inside the epilayer are weak. The spurious contributions of the backsides are suppressed in differentiated spectra.

56

Optical constants of AlAsSb Ava_AlAsSb-ReflTOTa

REFLECTIVITY

0.6

R590 (Montpellier), GaSb R595 (Montpellier)

0.5

0.4

0.3

GaSb, cap 10nm A2017 A2018

AlAsSb, 2000 nm GaSb, substrate

2

3

4

PHOTON ENERGY (eV)

The capped films of AlAsSb are transparent up to the visible range. The interference fringes provide fair sensitivity to both refractive index and film thickness. The capping layer influences strongly the spectra in NIR-VIS-UV range. In fact, above 3.5 eV, the penetration depth in GaSb is smaller than the cap thickness and the light does not see the ternary material.

57

Optical constants of AlAsSb AlAsSb-ReflFIR

1.0

REFLECTIVITY

0.8 0.6 0.4 A2017

0.2 A2018

0.0 0

200

400

600 -1

WAVENUMBER (cm )

The FIR spectra of GaSb/AlAsSb/GaSb samples are rather complex, displaying the free carriers and lattice vibration of the substrate and cap GaSb, as well as the lattice vibration and (less clearly) free carriers in AlAsSb. The measured spectra (solid lines) can be fitted fairly well (dotted lines) assuming the Drude-Lorentz response of the substrate, film, and cap layer. There seems to be no clear signature of the significantly higher free-carrier density in A2018 compared to A2017, the target values being 5.2E17 and 2.3E18 cm-3, respectively. 58

Optical constants of AlAsSb AlAsSb-ReflMIR

REFLECTIVITY

0.40

A2017

0.35

0.30

0.25 A2018

0.20 1000

2000

3000

4000

5000

6000

-1

WAVENUMBER (cm )

The MIR spectra of GaSb/AlAsSb/GaSb samples are dominated by the interference within the ternary layer, with possible inclusion of the light reflected on the backside of the (transparent) substrate. 59

Optical constants of AlAsSb Ava_AlAsSb-ReflNIRa

A2017

REFLECTIVITY

0.45

dAlAsSb = 1869  2 nm dcap

= 7.4  0.2 nm

A2018

dAlAsSb = 1853  2 nm dcap

= 6.9  0.2 nm

0.40 0.35 0.30 0.25 1.2

1.3

1.4

1.5

1.6

PHOTON ENERGY (eV)

The NIR spectra of GaSb/AlAsSb/GaSb are free from the spurious reflections on the backside of the substrate; they are suitable for a precise determination of film thicknesses from the fits (lines) of the measured data (symbols) using the twolayer GaSb-AlAsSb-GaSb(cap) system. 60

Optical constants of AlAsSb Ava_AlAsSb-ReflNIRm

0.55 R595 (Montpellier)

dcap

0.50 REFLECTIVITY

dAlAsSb = 1968  2 nm = 12.9  0.2 nm

0.45 0.40 0.35 0.30

1.2

1.3

1.4

1.5

1.6

PHOTON ENERGY (eV)

The NIR spectra of GaSb/AlAsSb/GaSb samples are free from the spurious reflections on the backside of the substrate; they are suitable for a precise determination of film thicknesses from the fits (lines) of the measured data (symbols) using the twolayer GaSb-AlAsSb-GaSb(cap) system.m Note the higher-lying envelope for the R595 sample, which is due to the thicker cap layer.

61

Optical constants of GaSb:Te and AlAsSb and evaluation of effective DBR layer thickness Summary of the target and optically measured film thicknesses Film thickness d in nm ====================== (error estimate in nm in parantheses) epilayers GaSb:Te/GaSb sample A1978 A1979 A1985 A1986

Te_content d(growth) d(optical) 5E17 2000 1914(10) 2.5E18 2000 1980(25) 1E18 1970 1950(20) 4E18 1970 1990(30)

epilayers GaSb_subs/AlAsSb/GaSb_cap

sample A2017 A2018

AlAsSb d(growth) d(optical) 1925 1869(2) 1925 1853(2)

GaSb_cap d(growth) d(optical) 10 7.4(0.2) 10 6.9(0.2) 62

Noise measurement I-V and noise characteristics have been measured on NEMIS samples A 1847 and A 1853 (CW lasers from WSI) and A 1883 and A 1884 (pulsed laser from UM2). All these lasers were supplied on a provisional TO 46 headers with an optical window.

IF / A

I-V characteristics:

10

-1

10

-3

10

-5

10

-7

10

-9

A1884 A1883 A1853 A1847 T=300K

0.5

1.0

1.5

UF / V

63

Noise measurement

Results of noise measurements:

-12

10

-14

10

-16

10

-18

10

-11

A1883 T=300K f =1kHz

100k 10k 1k 100 0

0.4

0.8 UF / V

-13

10

-15

10

-17

2

2

Su / V s

A1853 T=300K f =1kHz

10 Su / V s

10

1.2

100k 10k 1k 100 0

0.5

1.0

1.5

UF / V

64

High resolution absorption spectra of CH4 and CO measurement for WSI and Siemens According demands from WSI and Siemens absorption spectra of selected gases – CH4 and CO (CO2 is under investigation) within the NEMIS spectral range were measured at lower and higher pressures at wavenumbers between 2000 and 6200 cm-1 with resolution of 0.01 or 0.02 cm-1. We have used spectrometer Brucker IFS 120 (highest resolution 0.001 cm-1 was not necessary to use). Gas pressures were from 1.5 to 60 torr. Influence of pressure up to 1 bar in the NEMIS spectral range on width of absorption lines will be studied during the third year of the project.

65

High resolution absorption spectra of CH4 and CO measurement for WSI and Siemens 1.6

5 4.5 4

3.5

3

2.5  [m]

1.5

Absorption spectra of selected gases were measured at low pressures and wavenumbers between 2000 and 6200 cm-1

CH4

1.4 1.2 1.0 0.8 0.6 0.4

1.55 Torr A=A+0.15 2.93 Torr A=A+0.10 6.12 Torr A=A+0.05 60 Torr

0.2 0.0 2000

2500

3000

3500

4000

4500

5000

5500

6000

6500

7000

-1

W [cm ]

1.8

5 4.5

4

3.5

3

2.5

 [m]

2

1.5

CO

1.6 1.4

A [arb. u.]

A [arb. u.]

2

1.2 1.0 0.8 0.6

1.5 Torr A=A+0.10 2.4 Torr A=A+0.05 5 Torr

0.4 0.2 0.0 2000

2500

3000

3500

4000

4500

5000

5500

6000

6500

7000

-1

W [cm ]

66

High resolution absorption spectra of CH4 and CO measurement for WSI and Siemens 2.32 1.6

2.31

 [m]

2.3

1.6

CH4

1.4

1.55 Torr A=A+0.15 2.93 Torr A=A+0.10 6.12 Torr A=A+0.05 60 Torr

1.2

2.314

2.3132

2.3124

2.3116

1.0

A [arb. u.]

0.6

0.8 1.55 Torr A=A+0.15 2.93 Torr A=A+0.10 6.12 Torr A=A+0.05 60 Torr

0.6

0.4

0.4

0.2

0.2

0.0 4320

4325

4330

0.0 4321

4335

4322

4323

 [m]

-1

W [cm ] 1.6

2.31

1.2

0.8

4315

2.3108

CH4

1.4

1.0

2.3125 2.31225

2.312

4324

4325

4326

4327

4328

4329

-1

2.31175 2.3115 2.31125

2.311

2.31075 2.3105 2.31025

W [cm ]

CH4

1.4 1.2

A [arb. u.]

A [arb. u.]

 [m]

2.29

1.0 0.8 1.55 Torr A=A+0.15 2.93 Torr A=A+0.10 6.12 Torr A=A+0.05 60 Torr

0.6 0.4 0.2 0.0 4324.0

4324.5

4325.0 -1

W [cm ]

4325.5

4326.0

67

High resolution absorption spectra of CH4 and CO measurement for WSI and Siemens  [m] 2.35 1.2

2.34

2.33

2.32

2.31

2.3

2.29 2.32 1.2

2.315

2.31

2.305

CO

 [m]

2.3

2.295

2.29

CO

A [arb. u.]

A [arb. u.]

1.0

0.8

1.0

1.5 Torr A=A+0.10 2.4 Torr A=A+0.05 5 Torr

0.8

4320

4330

4340

4350

4360

-1

W [cm ] 1.5 Torr A=A+0.10 2.4 Torr A=A+0.05 5 Torr

0.6

4260 4270 4280 4290 4300 4310 4320 4330 4340 4350 4360  [m]

-1

W [cm ]

1.2

2.3325

2.332

2.3315

2.331 1.2

 [m]

2.3305 2.32

CO

2.319

2.318

CO

A [arb. u.]

A [arb. u.]

1.0 1.0

0.8

1.5 Torr A=A+0.10 2.4 Torr A=A+0.05 5 Torr

0.6 4287

4288

4289 -1

W [cm ]

1.5 Torr A=A+0.10 2.4 Torr A=A+0.05 5 Torr

0.8

4290

4310

4311

4312

4313 -1

W [cm ]

4314

Laser ageing measurement

Laser ageing measurement Time dependence of optical power output of studied pulse lasers. A1883 40mA A1884 30mA 1s/100kHz

2.4 2.2

Output Power [a.u.]

2.0 1.8 1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0.0 0

120

240

360

480

600

720

840

960

TIME [hours] 70

Laser ageing measurement Glued pulse laser instability during first 500 hours A1884 1us/100kHz/30mA 080912T0 080915T2 080916T4 080917T6 080918T8

2.5 2.4

16.9.2008 9:15÷10:15 h.

A1883 1us/100kHz/40mA 080902T1 080903T3 080905T5 080908T7 080910T9

1.80

17.9.2008 10:00-11:00 h.

1.80

18.9.2008 9:00÷10:00 h.

16.9.2008 10:15÷11:15 h.

2.3

1.75

1.75

15.9.2008 10:15÷11:15 h.

2.2

1.70 17.9.2008 9:00÷10:00 h.

1.9

15.9.2008 9:15÷10:15 h.

1.8 1.7 1.6 12.9.2008 9:15÷10:15 h.

1.5 1.4

1.70

8.9.2008 10:50÷11:50 h.

12.9.2008 10:15÷11:15 h.

1.65 5.9.2008 10:30÷11:30 h.

1.60 3.9.2008 8:30÷ 9:30 h.

1.55

2.9.2008 14:30÷15:30 h.

STABILITY [mV]

2.0

STABILITY [mV]

STABILITY [mV]

2.1

1.65

1.60

A1883 1us/100kHz/40mA 080912T1 080915T3 080916T5 080917T7 080918T9

1.55

1.50

1.50

1.45

1.45

1.3 1.2 1.1

18.9.2008 10:00÷11:00 h.

10.9.2008 11:15÷12:15 h.

1.0

1.40

1.40 0

600

1200

1800

2400

TIME [s]

3000

3600

0

600

1200

1800

2400

TIME [s]

3000

3600

0

600

1200

1800

2400

3000

3600

TIME [s]

71

Laser ageing measurement Laser instability significantly decreases after 500 hours A1883 1us/100kHz/40mA 080929T1 080930T3 081001T5 081002T7 [mV]

A1884 1us/100kHz/30mA 081006T0 081008T2

1.80

2.4 2.3 2.2 8.10.2008 9:00÷10:00 h.

2.1

6.10.2008 9:00÷10:00 h.

1.9 1.8 1.7 1.6 1.5

STABILITY [mV]

STABILITY [mV]

2.0

1.75

1.75

1.70

1.70

1.65

1.65

1.60 1.55 1.50

3.10.2008 10:00÷11:00 h. 1.10.2008 10:00÷11:00 h.

1.45

1.4

1.80

2.10.2008 10:00÷11:00 h.

STABILITY [mV]

2.5

A1883 1us/100kHz/40mA 081006T1 081008T3

1.60 1.55 1.50 1.45 6.10.2008 10:00÷11:00 h.

29.9.2008 10:15÷11:15 h.

1.3

1.40

1.40

1.35

1.35

1.2 1.1

30.9.2008 9:15÷10:15 h.

1.0 0

600

1200

1800

2400

TIME [s]

3000

3600

8.10.2008 10:00÷11:00 h.

1.30

1.30 0

600

1200

1800

2400

TIME [s]

3000

3600

0

600

1200

1800

2400

3000

3600

TIME [s]

72

WSI L-I-V measurement

• Light output-current-voltage (L-I-V) curve • Temperature dependent L-I curve • Information of the mode-gain offset • Differential series resistance • Differential quantum efficiency 73

WSI L-I-V measurement

Photograph showing the schematic representation of L-I-V measurement setup.

74

WSI Spectra Measurement

Vertex 70 FTIR (Bruker Optics GmbH) • Spectra measurements with high resolution • SMSR (Side Mode Suppression Ratio) • Stopband of the DBR • Characterization of the PL samples 75

WSI XRD Measurement

Inte ns ity (c ts /c )

10

4

S ubs tra te

10

3

10

2

10

1

10

0

10

AlS b/GaSb DBRs

Active re gion QW

-1

58

59

60

61

62

 (degree)

• Calibration of the MBE growth rate • Control of the quatum well strain • Information of the material composition

76

Deviations from WP4 plan/measures

•Small delay in ageing measurement due to delay of final NEMIS laser supply. Not important for final conclusions. •Not expected continuation of DBR material optical measurements, which will be continued in the third year, because interesting and publishable results can be obtained. Interesting dissemination of NEMIS related results, which can be interesting for other researchers and applicators.

77

WP4 deliverables/milestones • No deliverables or milestones in WP4 for this second year period.

78

WP4 near term plans • •

• •

MBE in-situ and ex-situ characterisations:WSI and UM2 – the same as during the second year Specific diagnostic and more precise characterisation: IOP with collaboration of WSI and UM2 - optical constants of Bragg mirror materials - GaSb:Te - measurement of the noise of lasers: IOP Ageing of laser sets: IOP, lasers supplied by VERTILAS, WSI and UM2 - work on the standard (industrial) degradation equipment VERTILAS Laser absorption spectroscopy (LAS) measurements: IOP – laser emission parameters change during ageing – preparation of calibration of VCSELs by LAS – exact measurement of selected gases at higher pressures

Comments Equipment, characterisation and diagnostic methods, results and conclusions which were incorporated in WP4 report by other partners will be (were) presented in detail by them during this meeting.

Thank you for your attention 80

Appendix 4

The NEMIS Project details

Devices processing 1 – Au/Ge/Ni top contact deposition

2 – Wet etching

3 – Isolation

4 – Contact report 5 – Substrate thinning and Au/Ge/Ni bottom contact deposition

Simple Simple and and fast fast process process

InAsSb InAsSb stop stop etch etch => => wall wall etching etching

Ring Ring electrodes electrodes with with several several internal internal diameters diameters :: 10µm, 10µm, 20µm, 20µm, 40µm, 40µm, 80µm 80µm and and 160µm 160µm

EP-VCSEL performances at 2.3 µm 2

15 400

10

5

200

Total diameter 60µm

200

220

240

260

280

0 300

Normalized optical power (dB)

Temperature (K) 0

11°C CW

28 mA 29mA 30 mA 31mA 32 mA

-5

2.3075

2.3100

0

200

400

11°C 13°C 15°C 17°C 19°C 20°C

2

600

800

1000

1200

2.3125

Wavelength (µm)

2.3150

2

CW

1 1

0

0

5

10

15

20

25

30

35

Current (mA)

I=0.31nm/mA

-10

2

0 180

Voltage (V)

Threshold Current (mA)

600

3

 Pulsed operation (3 µs/100 kHz) : • Operation above 300K (Jth~0.6 kA/cm2) • Jth min (0.3 kA/cm2) @ 250K  CW operation : • Maximum temperature 293K • Ith (CW) ~ 1 kA/cm2 @ 284K • Wavelength shift Δλ/ΔI = 0.31 nm/mA

Optical power (arb.un.)

Pulsed operation 3µs / 100kHz

Threshold Current Density (A/cm )

20

Current density (A/cm )

VCSEL Design p-contact

light

dielectrical mirror: 4 x Si / SiO2 (R = 99.7%)

active region: 5 Ga0.63InAsSb0.89 quantum wells Al0.33GaAsSb0.97 barriers (1.6% lattice mismatch) epitaxial mirror: 24 x AlAsSb / GaSb (R = 99.8%)

n-GaSb substrate

n-contact

buried tunnel junction (BTJ)

VCSEL Design - Field distribution ep i D taxi BR a l

3 -c av ity

di el D ect BR ric

2

3 |E |

re fra ctive inde x

4

2

a

1 0

pos ition

ive t c

re

on i g

J BT

VCSEL Results – L-I-V Characteristics 100 -10°C 0°C 10°C 20°C 30°C T

1.0

0.5

0.0

80 60 40

h

40°C 50°C 0

5

10

15

20 20

output powe r (µW)

volta ge (V)

1.5

8 µm

0

curre nt (mA)

continuous wave operation up to 50°C @ -10°C: = 2.3 mA  Ith  jth, eff

= 2.0 kA / cm2

 Uth

= 0.85 V

 Pmax

= 79 µW

CO Detection with GaSb-based BTJ-VCSEL norma lize d s e cond ha rmonic s pe ctrum (a .U.)

*

Wavelength Modulation Spectroscopy (WMS): small-signal wavelength modulation (f = 10 kHz) superimposed on a constant bias I0 = 7 mA

me a s ure d fit 2.324

2.326

57 ppm CO 2.328

wa ve le ngth (µm)

2.330

* Jia Chen et al. Siemens Corporate Technology, Power & Sensor Systems

 first gas absorption measurements have been performed  57 ppm CO detection @ 2.33 µm by Siemens Corporate Technology

Appendix 5 MOVPE laboratory MIR co-operations 1) ČVUT Praha – FEL

13) ÚRE/ÚFE AVČR Praha

2) VUT Brno – FStavební

14) Univ. Porto, Portugal

3) Montpellier University, France

15) S-Y-S University, Kao-Shung, Taiwan

4) NanoPLUS, Germany 5) VŠCHT Praha - FCHI - ÚFCH 6) EMF Limited, UK 7) ÚFCH AVČR Praha 8) MU Brno - PřF - ÚFPF 9) EU SAV Bratislava Slovakia 10)

Budapešť, Hungary

11) FTI A.F.Ioffe St. Petersburg Russia 12) MFF UK Praha

Red = MidInfrared, (Partly) Blue - other cooperations (QD mainly)