Nanotechnologie Studijní program: 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 Vpřednášce 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 Wavelength ( m) Energy (ev) Frequency (THz) Wavenumber (cm -1 ) Visible Near Infrared (NIR) Mid Infrared (MIR) Far Infrared (FIR or THz) mm Wave 0.4-0.7 0.7-2.0 2.0-20 20-1000 >1000 1.7-3.1 0.6-1.7 0.06-0.6 0.001-0.06 <0.001 400-750 150-400 15-150 0.3-15 <0.3 14000-25000 5000-14000 500-5000 10-500 <10
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 od2do20μm, 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 A III B V 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)
GaAs: buffer 230 nm AlGaAs-n typ 570 nm AlGaAs 400 nm GaAs 150 nm AlGaAs 320 nm AlGaAs-p typ 570 nm GaAs 700 nm GaAs:Te substrate SPSLS 12x (InAs / GaAs)
Srovnání laserů s ternární a supermřížkovou (MQW) aktivní oblastí Ternární InGaAs QW laser InAs/GaAs laser se supermřížkou Optical Power [a.u.] 200 150 100 50 0 Intensity 1.0 0.8 0.6 0.4 0.2 0.0 EL I ex =2 A I ex =2.25 A I ex =2.5 A I ex =3 A T=300 K 1.1 1.2 1.3 1.4 Emission Energy [ev] T 0 = 109 K laser A 25 o C 40 o C 50 o C 60 o C 70 o C 80 o C 85 o C Optical Power [ W] 120 100 80 60 40 20 0 Intensity 1.0 0.8 0.6 0.4 0.2 0.0 PL EL I ex =0.46A T=300K 1.1 1.2 1.3 1.4 Emission Energy [ev] T 0 = 126 K laser B 25 C 35 C 45 C 55 C 65 C 75 C 85 C 0 1000 2000 3000 4000 5000 6000 Current Density [A/cm 2 ] 0 100 200 300 400 500 600 Current Density [A/cm 2 ]
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 1200 1000 800 600 400 200 25 C 50 C 0 0 10 20 30 40 50 Excitation Current [ma] 0-10 EL Intensity [db] -20-30 -40-50 -60-70 -80 T=25 C T=50 C T=70 C I ex =70 ma -90 2340 2360 2380 2400 2420 2440 2460 2480 Wavelength [nm]
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
Application: trace gas sensing Outline 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, (CH 4 and NH 3 detection at 2.3 µm, HF at 2.5 µm, ) Single frequency, P > 1 mw, CW, RT lasers VCSELs NEMIS project : EP GaSb-based VCSEL 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
Current Density (ka/cm 2 ) State of the art before NEMIS 1 st 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 I th >2kA/cm 2 (A. Baranov et al., Electronics Letters, 1998, Vol.34, p. 281) 1.0 0.8 0.6 0.4 0.2 0.0-0.2-0.4-0.6 p-doped n-doped -3-2 -1 0 1 2 3 4 Voltage (V) Contact diameter: 200 µm MQW Active region n-dbr n-contact p-contact p-dbr GaSb n-substrate Voltage drop per pair @ 1 ka/cm 2 : Te-doped DBR ~ 25 mv/pair Be-doped DBR ~ 155 mv/pair Optical losses : Te-doped DBR ~ 5 10 cm -1 Be-doped DBR > 40 cm -1 * Perona et al. Semi. Sc. Tech (22), 2007 PIN structure no optimized for RT CW operation
Buried Tunnel Junction p + GaSb:Si n + InAsSb:Si n + p + energy = 2.5 10-6 cm 2 with n = 1 10 19 cm 3 + - position Substitution: p-doped by n-doped material reduced electrical resistance lower absorption losses
Buried Tunnel Junction p + GaSb:Si p + energy space charge region n n + p + position blocking pn-junction current confinement by diameter d 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 (2 nd 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 1.0 0.8 2.5x10 18 5x10 17 FIRrefl-FIRR1 REFLECTANCE 0.6 0.4 1x10 18 N f = 4x10 18 cm -3 0.2 GaSb:Te (2 m, N f ) / GaSb:Te (N s =2.5x10 17 cm -3 ) 0.0 0 200 400 600 WAVENUMBER (cm -1 ) 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 W gap, bare substrate, 2.5x10 17 cm -3 0.360 REFLECTANCE 0.355 5x10 17 1x10 18 2.5x10 18 N f = 4x10 18 cm -3 0.350 GaSb:Te (2 m, N f ) / GaSb:Te (N s =2.5x10 17 cm -3 ) 5500 6000 6500 7000 W (cm -1 ) 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 0.0002 N f = 4x10 18 cm -3 2.5x10 18 1x10 18 5x10 17 E g MIRrefl-DerR2 bare substrate, 2.5x10 17 cm -3 dr/dw (cm) 0.0000-0.0002 GaSb:Te (2 m, N f ) / GaSb:Te (N s =2.5x10 17 cm -3 ) 2000 4000 6000 W (cm -1 ) 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 0.6 R590 (Montpellier), GaSb REFLECTIVITY 0.5 0.4 R595 (Montpellier) GaSb, cap 10nm 0.3 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 1.0 AlAsSb-ReflFIR 0.8 REFLECTIVITY 0.6 0.4 0.2 0.0 A2017 A2018 0 200 400 600 WAVENUMBER (cm -1 ) 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 0.40 A2017 REFLECTIVITY 0.35 0.30 0.25 0.20 A2018 1000 2000 3000 4000 5000 6000 WAVENUMBER (cm -1 ) 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 0.45 A2017 d AlAsSb = 1869 2 nm d cap = 7.4 0.2 nm A2018 d AlAsSb = 1853 2 nm d cap = 6.9 0.2 nm REFLECTIVITY 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 0.55 0.50 R595 (Montpellier) d AlAsSb = 1968 2 nm d cap = 12.9 0.2 nm Ava_AlAsSb-ReflNIRm REFLECTIVITY 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 Te_content d(growth) d(optical) A1978 5E17 2000 1914(10) A1979 2.5E18 2000 1980(25) A1985 1E18 1970 1950(20) A1986 4E18 1970 1990(30) epilayers GaSb_subs/AlAsSb/GaSb_cap AlAsSb GaSb_cap sample d(growth) d(optical) d(growth) d(optical) A2017 1925 1869(2) 10 7.4(0.2) A2018 1925 1853(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. 10-1 I-V characteristics: 10-3 I F / A 10-5 10-7 A1884 A1883 A1853 A1847 T=300K 10-9 0.5 1.0 1.5 U F / V 63
Noise measurement Results of noise measurements: S u / V 2 s 10-12 10-14 10-16 10-18 A1853 T=300K f =1kHz 100k 10k 1k 100 0 0.4 0.8 1.2 S u / V 2 s 10-11 10-13 10-15 10-17 A1883 T=300K f =1kHz 100k 10k 1k 100 0 0.5 1.0 1.5 U F / V U F / V 64
High resolution absorption spectra of CH 4 and CO measurement for WSI and Siemens According demands from WSI and Siemens absorption spectra of selected gases CH 4 and CO (CO 2 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 CH 4 and CO measurement for WSI and Siemens [ m] 2.32 2.31 2.3 2.29 1.6 1.4 1.2 CH4 1.55 Torr A=A+0.15 2.93 Torr A=A+0.10 6.12 Torr A=A+0.05 60 Torr 1.6 1.4 1.2 [ m] 2.314 2.3132 2.3124 2.3116 2.3108 2.31 CH4 A [arb. u.] 1.0 0.8 0.6 0.4 A [arb. u.] 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 0.2 0.0 0.0 4315 4320 4325 4330 4335 4321 4322 4323 4324 4325 4326 4327 4328 4329 W [cm -1 ] [ m] 2.3125 2.31225 2.312 2.31175 2.3115 2.31125 2.311 2.31075 2.3105 2.31025 W [cm -1 ] 1.6 1.4 CH4 1.2 A [arb. u.] 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 4324.0 4324.5 4325.0 4325.5 4326.0 W [cm -1 ] 67
High resolution absorption spectra of CH 4 and CO measurement for WSI and Siemens [ m] 2.35 2.34 2.33 2.32 2.31 2.3 2.29 1.2 CO [ m] 2.32 2.315 2.31 2.305 2.3 2.295 2.29 1.2 CO A [arb. u.] 1.0 A [arb. u.] 1.0 0.8 0.8 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 W [cm -1 ] 1.2 1.5 Torr A=A+0.10 2.4 Torr A=A+0.05 5 Torr [ m] 2.3325 2.332 2.3315 2.331 2.3305 [ m] 2.32 2.319 2.318 1.2 CO 4320 4330 4340 4350 4360 W [cm -1 ] CO 1.0 A [arb. u.] A [arb. u.] 1.0 0.8 0.6 1.5 Torr A=A+0.10 2.4 Torr A=A+0.05 5 Torr 0.8 1.5 Torr A=A+0.10 2.4 Torr A=A+0.05 5 Torr 4287 4288 4289 4290 4310 4311 4312 4313 4314 W [cm -1 ] W [cm -1 ]
Laser ageing measurement
Laser ageing measurement Time dependence of optical power output of studied pulse lasers. 2.4 A1883 40mA A1884 30mA 1 s/100khz 2.2 2.0 Output Power [a.u.] 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 2.5 2.4 2.3 A1884 1us/100kHz/30mA 080912T0 080915T2 080916T4 080917T6 080918T8 16.9.2008 9:15 10:15 h. 18.9.2008 9:00 10:00 h. 1.80 1.75 A1883 1us/100kHz/40mA 080902T1 080903T3 080905T5 080908T7 080910T9 1.80 1.75 17.9.2008 10:00-11:00 h. 16.9.2008 10:15 11:15 h. 15.9.2008 10:15 11:15 h. 2.2 2.1 1.70 8.9.2008 10:50 11:50 h. 1.70 2.0 17.9.2008 9:00 10:00 h. 12.9.2008 10:15 11:15 h. STABILITY [mv] 1.9 1.8 1.7 1.6 1.5 1.4 1.3 15.9.2008 9:15 10:15 h. 12.9.2008 9:15 10:15 h. STABILITY [mv] 1.65 1.60 1.55 1.50 5.9.2008 10:30 11:30 h. 3.9.2008 8:30 9:30 h. 2.9.2008 14:30 15:30 h. STABILITY [mv] 1.65 1.60 1.55 1.50 A1883 1us/100kHz/40mA 080912T1 080915T3 080916T5 080917T7 080918T9 1.2 1.45 1.45 1.1 1.0 0 600 1200 1800 2400 3000 3600 TIME [s] 1.40 10.9.2008 11:15 12:15 h. 0 600 1200 1800 2400 3000 3600 TIME [s] 1.40 18.9.2008 10:00 11:00 h. 0 600 1200 1800 2400 3000 3600 TIME [s] 71
Laser ageing measurement Laser instability significantly decreases after 500 hours 2.5 2.4 2.3 A1884 1us/100kHz/30mA 081006T0 081008T2 1.80 1.75 A1883 1us/100kHz/40mA 080929T1 080930T3 081001T5 081002T7 [mv] 1.80 1.75 A1883 1us/100kHz/40mA 081006T1 081008T3 STABILITY [mv] 2.2 2.1 2.0 1.9 1.8 1.7 1.6 1.5 1.4 1.3 8.10.2008 9:00 10:00 h. 6.10.2008 9:00 10:00 h. STABILITY [mv] 1.70 1.65 1.60 1.55 1.50 1.45 1.40 3.10.2008 10:00 11:00 h. 1.10.2008 10:00 11:00 h. 2.10.2008 10:00 11:00 h. 29.9.2008 10:15 11:15 h. STABILITY [mv] 1.70 1.65 1.60 1.55 1.50 1.45 1.40 6.10.2008 10:00 11:00 h. 1.2 1.1 1.0 0 600 1200 1800 2400 3000 3600 TIME [s] 1.35 1.30 30.9.2008 9:15 10:15 h. 0 600 1200 1800 2400 3000 3600 TIME [s] 1.35 1.30 8.10.2008 10:00 11:00 h. 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 Intens ity (cts /c) 10 4 Substrate AlS b/gas b 10 3 DBRs 10 2 10 1 10 0 Active region QW 10-1 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 and fast process InAsSb stop etch => wall etching Ring electrodes with several internal diameters : 10µm, 20µm, 40µm, 80µm and 160µm
EP-VCSEL performances at 2.3 µm Threshold Current (ma) 20 15 10 5 Pulsed operation 3µs / 100kHz Total diameter 60µm 0 0 180 200 220 240 260 280 300 Temperature (K) 600 400 200 Threshold Current Density (A/cm 2 ) Voltage (V) 0 200 400 600 800 1000 1200 3 2 2 1 11 C 13 C 15 C 17 C 19 C 20 C Current density (A/cm 2 ) CW 0 0 5 10 15 20 25 30 35 Current (ma) 1 Optical power (arb.un.) Normalized optical power (db) 0-5 -10 11 C CW I=0.31nm/mA 2.3075 2.3100 2.3125 2.3150 Wavelength (µm) 28 ma 29mA 30 ma 31mA 32 ma Pulsed operation (3 µs/100 khz) : Operation above 300K (J th ~0.6 ka/cm 2 ) J th min (0.3 ka/cm 2 ) @ 250K CW operation : Maximum temperature 293K I th (CW) ~ 1 ka/cm 2 @ 284K Wavelength shift Δλ/ΔI = 0.31 nm/ma
VCSEL Design p-contact dielectrical mirror: 4 x Si / SiO 2 (R = 99.7%) light active region: 5 Ga 0.63 InAsSb 0.89 quantum wells Al 0.33 GaAsSb 0.97 barriers (1.6% lattice mismatch) epitaxial mirror: 24 x AlAsSb / GaSb (R = 99.8%) n-gasb substrate n-contact buried tunnel junction (BTJ)
BTJ active region VCSEL Design - Field distribution epitaxial DBR 3 -cavity dielectric DBR 4 3 2 1 0 position refractive index E 2
VCSEL Results L-I-V Characteristics voltage (V) 1.5 1.0 0.5 20 C 30 C 40 C -10 C 0 C 10 C T h 50 C 0.0 0 5 10 15 20 100 80 60 40 20 0 output power (µw) 8 µm curre nt (ma) continuous wave operation up to 50 C @ -10 C: I th = 2.3 ma j th, eff = 2.0 ka / cm 2 U th = 0.85 V P max = 79 µw
CO Detection with GaSb-based BTJ-VCSEL normalized s e cond harmonic spectrum (a.u.) measured fit 2.324 2.326 2.328 2.330 wavelength (µm) 57 ppm CO * Wavelength Modulation Spectroscopy (WMS): small-signal wavelength modulation (f = 10 khz) superimposed on a constant bias I 0 = 7 ma * 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)