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 1s/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)