2015

Preparation of semiconductor nanomaterials 2014/2015 (prof. E. Hulicius, FZÚ AV ČR, v.v.i.,)

11. Semiconductor lasers (LD). Lesson about fluent and step parameter LDs (and LEDs) improving due to introduction of nanostructures (Quantum Wells and Dots – QW, QD). Inside of the LD and LED structures there are used very interesting nanostructures nowadays . Their more detail description can help students to understand principles of other devices.

12. Light emitting diodes (LED). The same as about LDs.

Applications according the spectral regions We can divide the spectrum fields according applications and materials: The main fields -

visible and near infrared

Here are known and mature materials and widely used applications under producer the applied research. Here is a field for important and interesting improvements, but I do not expect crucial „break through“. Adjacent spectral fields – ultraviolet (nitrides, ZnO, diamond, ...? – many interesting applications) mid-infrared (will be described in detail later)

Definition of the spectral fields of LED and LD emission Below used function wavelenght , energy E, frequency f a wave number  relations: 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)

Applications according the spectral regions We can divide the spectrum fields according applications and materials:

The main fields -


Here are known and mature materials and widely used applications under producer the applied research. Here is a field for important and interesting improvements, but I do not expect crucial „break through“. Adjacent spectral fields – ultraviolet (nitrides, ZnO, diamond, ...? – many interesting applications) mid-infrared (will be described in detail later)

Examples of optoelectronic applications in the visible region



Industrial MOVPE technology

Industrial MOVPE technology

Applications according the spectral regions We can divide the spectrum fields according applications and materials: The main fields -


Here are known and mature materials and widely used applications under producer the applied research. Here is a field for important and interesting improvements, but I do not expect crucial „break through“. Adjucent spectral fields – ultraviolet (nitrides, ZnO, diamond, ...? – many interesting applications)

mid-infrared (will be described

in detail later)

Mid-infrared region of the electromagnetic radiation is usually defined from 2 do 20 μm. It is important from application point of view: •Detection and exact and sensitive concentration measurements of different materials (mainly atmospheric pollutants and industrial gases by laser absorption spectroscopy; •In medicine - diagnostic – composition and impurities in breath, •And therapy – activation of drugs by MIR radiation, which can penetrate into a body; •„Free space" communication (atmospheric window); •Conversion of radiation to electric energy (thermophotovoltaics); •Military – atmospheric window for laser weapons; detectors; sensitive thermovision; detection of explosives poisons e.g.; MIR gates for advanced object protection. ------------------The firs applications were developed for fluoride fibre communication in MIR region with much lower absolute signal attenuation to compare to quartz fibres (fibres – Dianov in FIAN; lasers - FIAN, GIREDMET,…)

Forbidden gap dependence on lattice constant for some semiconductor materials

In1-xGaxAsyP1-y Equation for parameters in general of quaternary semiconductors ( = linear combination of parameters of binar compounds): p(x,y) = (1-x)(1-y)pInP + (1-x)ypInAs + xypGaAs + x(1-y)pGaP a(x,y) = 5.8688 - 0.4176x + 0.1895y - 0.0126xy Relation for forbidden gap of the quaternary semiconductors: Eg(x,y) = 1.35 + 0.672x - 1.091y + 0.758x2 + 0.101y2 + 0.111xy - 0.58x2y - 0.159xy2 + 0.268x2y2

. Dependence of energy of forbidden gap on compound composition

Some of older IR materials:

MIR region is very interesting from the material engineering and nanotechnoology. There are used quantum effect for new type of devices: •"W" structures of heterojunctions of type II. – elimination of the undesirable Auger recombination; •Quantum cascade lasers – evidently of the current most sophisticated semiconductor devices; wavelength is controlling by geometry and architecture of structure. •negative luminescence – remarkable effect with interesting applications;

LED Light Emitting Diode

1907(!) – The first electroluminescent diode - SiC, H.J. Round – (c) (Rediscovered by Losevem at 1928). 1936 - Destriau - LEDs from ZnS. 1952 - Welker – introduction of AIIIBV (GaAs). 1962 - Lasers (RCA, GE, IBM, MIT). 60-80-th- Expansion of epitaxial technologies. 70-90-th– Implementation of heterostructures and quantum wells. 1977 – Solving of the laser degradation and diodes (dislocation free substrates).

Recombination and biases

Electroluminescent materials

Heterojunctions – other point of view

(a) – well (trap) for electrons and holes (not yet quantum) (b) – quantum well with electron levels

LED structure with triple quantum well and electron blocking layer

Emmisson spektrum of LED

?

The main problem of LEDs is a light exit!!

How to solve it??

Heterostructure has influence also for LEDs – not only form the boundary (confine) of its active layer and ... ?

... It is transparent,

?

but …

... It is necessary to do something with shape -

And external efficiency will be improved.

?

And what about contacts ...

... Also its geometry is important.

Sometimes there are troubles with absorbed substrate.

?

Antireflex covering improve efficiency and also lifetime.

Mirrors, which are a part of the resonator can be also created in the structure.

But we have to be careful about lifetime and internal strain.

Colours have fundamental importance for applications. It can be solved not only by materials (composition of ternary and quaternary compounds), but in the case of nanostructures also by its size and geometry. Visible and Near Infrared regions are mainly commercional task now. Mid and Far IR or ultraviolet regions are subject of intensive research.

Improving of LEDs in time:

Blue LEDs – why so late? The road to white.

White diodes.

Two-colour diodes (in one chip!)

Also LEDs can work with resonator.

What is a cost of one lumen?

Spectral sensitivity of eye and LEDs properties.

LD Laser Diode and Semiconductor lasers – it is nearly the same, but not quite (there are also semiconductor lasers without P-N junction – pumped by light).

Laser jako prvek se zpětnou vazbou.

Pásová struktura jednoduchý p-n přechod, injekce elektronů.

Laserový čip – hetrorostruktura, vlnovod, rezonátor.

Vlnovod.

Heterogenous structures (heterostructures) - „clasical" Not only heterosturctures with P-N junctions, there are use homo-heterostructures with Eg junctions or fluent changes of forbidden gaps, refraction index with strong improvement of device parameters. Figures from Scientific American at 1971!! Obr Junctions type I., II. (a III.). Obr Strained junctions. Obr

Pásová struktura a index lomu.

Proužková geometrie a vlnovod.

Tvar výstupního optického svazku.

Types of the laser resonators:

Stripe geometry Confinement by: - Contact. - Contact and etching. -Cross P-N junction. - contact + etching + P-N junction + the second epitaxy,.

Spontaneous and stimulated emission

Gain and loss in dependence on photon energy for different electron concentrations in the active layer.

Lasing starts at long wave site of spectrum (due to absorption).

Heterojunctions – can create region where inversion of carrier population can be created more easy.

Due to heterojunctions can be created a waveguide:

Watt/Amper (exactly Watt/Watt) characteristic From it we can establish threshold, power, pumping energy, efficiency, differential efficiency and quantum differential efficiency.

Density of threshold current Jth State equation

dn/dt = J/ed – G(n)S – n/τ

n, e = concentration electrons, d = thickness of the active layer, G = gain, S = optical density, τ = lifetime of electrons, τ´ = lifetime of photons can be described under threshold:

dn/dt = J/ed – n/τ

and in equilibrium (d/dt = 0) is

n = J τ/ed

When electron concentration n increase to threshold concentration nth it is possible to write threshold current :

Jth = ednth /τ

Threshold concentration of the electrons nth it is possible to write:

nth = 1/Γgτ´ + n0 Γ = is optical bonding factor, g = coefficient of differential gain. Than it is:

Jth = ednth /τ´ = ed/τ (1/Γgτ´ + n0)

Thickness of active region define region where inversion of carrier population can be created more easy. It defined also thickness of waveguide.

x = amount of Al in AlGaAs barrier

Output from waveguide

Fabry-Perrot resonator: R = reflectivity; T = transmitivity P = optical power; L = length of resonator.

Temperature dependency of threshold current

Empirically found temperature dependency of threshold current The hotter the temperature the later the lasing (and usually worse efficiency). Dependence on material is visible.

Jth = Jth0exp(Tj/T0) Tj = temperature of active region. T0 = characteristic temperature, which show dependence of Jth on temperature. T0 can be different foe different temperature regions (Eg = f(T)). Tc = „break“ point.

Cooperation with FEL ČVUT a FZÚ AV ČR:

Optical Power [a.u.]

6 0 °C 7 0 °C 8 0 °C 9 0 °C

1 0 0 °C

0 ,2

0 ,4

0 ,6

0,5

5 Ls

2

4 0 °C 5 0 °C

0 ,0

1000

Current Threshold Density [A/cm ]

2 5 °C 3 0 °C

0 ,8

1 ,0 -2

C u rre n t d e n s ity [k A c m ]

The temperature variations of the dependence of laser optical output power on excitation current density for lascer with 7  InAs layers and thickness of SL~7.9 nm.

0,4

T0~ 90 K 0,3 100

T0 ~ 160 K

0,2

0,1

10

0

50

100

150

200

250

300

Differential Quantum Efficiency

733 7  In A s la y e rs S L ~ 7 .9 n m

0,0 350

Temperature [K]

Temperature dependence of threshold current density and differential quantum efficiency for laser with 5  InAs layers.

External resonator (a) noticeable improves monochromaticity (b), but device lost the advantage of miniaturity, compactness (it is better to solve it inside the structure) (c). (c)

Solving of space coherence tasks in the case of miniature semiconductor lasers (Far-field spectra). (It is general trouble of the small cavities.)

Strain in the structures can influence a threshold current.

Resume LED relatively cheap, efficient, notdegrading light sources Further increasing of efficiency (to 90%) and power (up 10 W per chip). Cheap white colour, (tuneability of the colour temperature from blue to yellow); fundamental energy savings. Wavelength expansion to UV and MIR. „Multicolour“ chips for white colour.

LD versus classical lasers = analogy – vacuum electronics versus transistors? Wavelength expansion to UV and MIR (we are engaged in it), ... Further increasing of efficiency (more than 90%) and power (over 20W per chip). „Multicolour“ chip; parallel optical communication. Controlling of colour; laser spectroscopy. One photon sources for quantum communications, ... ; Lifetime, cost, …

Thank you for your attention

Appendix Our results in this field

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


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

Vlastnosti laserů s MQW v aktivní oblasti

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)

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)

Výhody KT

 Hustota stavů ve tvaru delta funkcí  snížení nezářivé rekombinace (Auger a IVBA)  Nižší prahová proudová hustota v laserech s KT  Lepší teplotní stabilita prahového proudu  Snížení nezářivé rekombinace na zrcadlech  KT umožňují dosáhnout emitované vlnové délky 1.3m v systémech InAs/GaAs

Proč jsou KT tak intenzivně studovány? KJ

KT

Hustota stavů v objemovém polovodiči, kvantové jámě a kvantové tečce 3D

(E)

2D 0D

E1 E2

E3

E4

E

Stranski-Krastanowův mód růstu Vysoce napnuté struktury: rozdíl v mřížkových konstantách kolem 7%

InAs GaAs

Charakterizace a diagnostika epitaxního růstu a nanostruktur Mikroskopie meziatomárních sil AFM (Atomic Force Microscopy) Je vhodná i pro nevodivé vzorky. Nepožadujeme-li atomární rozlišení, je to relativně malá aparatura (ceny od 2 do 10 MKč) Rastrovací tunelová mikroskopie STM (Scanning Tunneling Microscopy) Je zapotřebí vzorky alespoň trochu vodivé. Dává atomární rozlišení, ceny podle vybavení od 0,5 do 20 MKč)

Zdroj: http://www.fzu.cz/texty/brana/atomy/spm1.php

TEM 7 vrstev KT, oddělovací vrstvy 7.5 nm

3 vrstvy KT, oddělovací vrstvy 3.7 nm

AFM

3 × QD

TEM 7 × QD 7 × QW

Kvantové tečky

Technologie přípravy: MOVPE 7. GaAs krycí vrstva 6. GaAs oddělovací vrstva 5. Přerušení růstu 30 s 4. InAs napnutá vtstva (1.4 ML) 3. GaAs podklad. vrstva 500 oC 2. GaAs podklad. vrstva 650 oC 1. GaAs substrát GaAs vrstvy: Prekursory TMGa a AsH3, celk. tlak 70 hPa, celk. průtok 8 l/min, teplota 650 oC a 500 oC, poměr V/III 150 a 43. InAs vrstvy: 50 ml/min H2/TMIn, poměr V/III 85, čas růstu 9 s, přerušení růstu 30 s.

KT překryté InGaAs KT překrytá GaAs Původní KT

KT překrytá InGaAs

Dosažená vlnová délka FL InAs/InGaAs KT

FL InAs/GaAs KT překrytých InGaAs InGaAs 23% In 45000 40000

InAs

1508B bez ternaru 1524B 13%In I*70 1527B 23%In 1526B 6%In I*35

35000 30000

GaAs

IPL(arb.u.)

25000 20000 15000

Základní stav:

10000

0.86 eV ……1.44 m

5000 0

1. excitovaný stav:

-5000 0.80

0.85

0.90

0.95

EPL(eV)

1.00

1.05

1.10

1.15

0.93 eV ……1.3 m

AFM picture of InAs/GaAs QDs

GaAs: buffer 230 nm

GaAs:Te substrate

AlGaAs-n typ 570 nm

AlGaAs 400 nm GaAs 150 nm

GaAs 150 nm

SPSLS 12x (InAs / GaAs)

AlGa As 320 nm

AlGaAs-p typ 570 nm GaAs 700 nm

Our diagnostic methods: • Nanocharacterisation - STM, AFM, TEM, • Photo and electroluminescence, • Magnetophotoluminescence, • Transport, • Photovoltaic absorption measurement, • Photocurrent spectroscopy, were used as the characterisation methods for the studying of parameters and optimisation of growth.

Naše výsledky a výstupy

MOVPE laboratory co-operations in 2005 1) ČVUT Praha - FEL 2) VUT Brno - FStavební 3) Montpellier University, France 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 13) ÚRE AVČR Praha 14) Univ. Porto, Portugal 15) S-Y-S University, Kao-Shung, Taiwan

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

Current results of the MOVPE laboratory, red = midinfra B Publications in the Refereed Scientific Journals in 2005/2006 (9 x z 16) [1] Pavel Hazdra, Jan Voves, Eduard Hulicius and Jiří Pangrác, Optical characterisation of MOVPE grown δ-InAs layers, in GaAs, phys. stat. sol. (c) 2 (2005) 1319-1324 1) ČVUT Praha - FEL [2] Chobola Z., Juránková V., Vaněk J., Hulicius E., Šimeček T., Alibert C. Rouillard Y., Werner. R, Noise spectroscopy measurement of 2.3 µm CW GaSb based laser diodes, Elektronika 1 (2005), pp.70-73, Poland ISSN 0033-2089 2) VUT Brno - FStavební, 3) Montpellier University, France, 4) NanoPLUS, Germany [3] M. Fulem, K. Růžička, V. Růžička, T. Šimeček, E. Hulicius J. Pangrác, J. Becker, J. Koch, A. Salzmann, Vapour pressure of Di-tert-butylsilan, J. of Chemical and Engineering Data C 50 (2005) 1613-1615 5) VŠCHT Praha - FCHI - ÚFCH, 6) EMF Limited, UK [4] S. Civiš, V. Horká, T. Šimeček, E. Hulicius, J. Pangrác, J. Oswald, O. Petříček, Y. Rouillard, C. Alibert, and R. Werner, GaSb based lasers operating near 2.3 μm for high resolution absorption spectroscopy, Spectrochimica Acta Part A 61 (2005) 3066-3069 7) ÚFCH AVČR Praha, Montpellier University, France, NanoPLUS, Germany [5] M. Fulem, K. Růžička, V. Růžička, T. Šimeček, E. Hulicius, and J. Pangrác, Vapour pressure measurement of metal organic precursors used for MOVPE, in press in J. Chem. Therm. (2005) VŠCHT Praha - FCHI - ÚFCH, [6] K. Kuldova; V. Krapek, A. Hospodkova, O. Bonaventurova-Zrzavecka, J. Oswald, E. Hulicius, J. Humlicek, Photoluminescence and magnetophotoluminescence of circular and elliptical InAs/GaAs quantum dots, in print, Mat. Sci. Eng. C, (2005) 8) MU Brno - PřF - ÚFPF [7] P. Hazdra, J. Voves, Hulicius, J. Pangrác, and Z. Šourek, Ultrathin InAs and Modulated InGaAs Layers in GaAs Grown by MOVPE Studied by Photomodulated Reflectance Spectroscopy, in print Appl. Surf. Science (2005) ČVUT Praha - FEL [8] František Dubecký, Eduard Hulicius, Secondo Franchi, Andrea Perďochová-Šagátová, Bohumír Zaťko, Pavel Hubík, Enos Gombia, Pavel Boháček, Jirka Pangrác, and Vladimír Nečas, Performance study of radiation detectors based on semi-insulating GaAs with P+ homo- and heterojunction blocking electrode, in print in Nuclear Instruments and Methods (2005) 9) EU SAV Bratislava Slovakia, 10) Budapešť Hungary [9] S. Civiš , V. Horká, J. Cihelka, T. Šimeček, E. Hulicius, J. Oswald, J. Pangrác, A. Vicet, Y. Rouillard, A. Salhi, C. Alibert, R. Werner and J. Koeth, Room temperature diode laser spectroscopy of near 2.3 µm, Apl. Phys. B 81 (2005) 857-861 ÚFCH AVČR Praha, Montpellier University, France, NanoPLUS, Germany [10] J. Oswald, J. Pangrác, E. Hulicius, T. Šimeček, K. D. Moiseev, M.P. Mikhailova, and Yu.P. Yakovlev, Luminescence of type II broken gap P-Ga0.84In0.16As0.22Sb0.78/p-InAs heterostructures with high mobility electron channel at the interface, J. Appl. Phys. 98 (2005) 11) FTI A.F.Ioffe St. Petersburg Russia [11] K.D. Moiseev, A.P. Astakhova, G.G. Zebrya, M.P. Mikhailova, Yu.P. Yakovlev, E. Hulicius, A. Hospodkova, J. Pangrác, K. Melichar, and T. Šimeček, Electroluminescence of AlSb/InAsSb/AlSb quantum well heterostructure grown by MOVPE, sent to Appl Phys Lett. (2005) FTI A.F.Ioffe St. Petersburg Russia [12] D. Kindl, P. Hubík, J. Krištofik, J.J. Mareš, E. Hulicius1, J. Pangrác, K. Melichar, Z. Výborný, and J. Toušková, Transport-controlling deep defects in MOVPE grown GaSb, sent to Semiconductor Science and Technology, (2006) 12) MFF UK Praha [13] A.Hospodková, K. Kuldová, E. Hulicius, J. Oswald, J. Pangrác, J. Zeman, V. Křápek, J. Humlíček, Luminescence and magnetophotoluminescence of vertically stacked InAs/GaAs quantum dot structures, sent to Phys Rev. B (2006) MU Brno - PřF - ÚFPF [14] K.D. Moiseev, A.P. Astakhova, G.G. Zebrya, M.P. Mikhailova, Yu.P. Yakovlev, E. Hulicius, A. Hospodkova, J. Pangrác, K. Melichar, and T. Šimeček, Qauntum well InAsSbP/InAsSb/AlAsSb laser heterostructures grown by combined MOVPE technology, prepared for Appl Phys Lett. (2006) FTI A.F.Ioffe St. Petersburg Russia [15] V. Křápek, K. Kuldová, J. Humlíček, A.Hospodková, J. Oswald, J. Pangrác, K. Melichar, E. Hulicius, Shape of InAs/GaAs quantum dot structures, AFM, prepared for APL (2006) MU Brno - PřF - ÚFPF [16] E. Samochin, H.H. Huang, J. Toušková, E. Hulicius, L-W. Tu, J. Pangrác, K. Jurek, I. Drbohlav, Model of transport in heavily strained InAs/GaAs quantum dot structures, prepared for Mat. Res and Eng. (2006) 12) MFF UK Praha, 15) S-Y-S University, Kao-Shung, Taiwan

Current results - 2005 D Papers at the International Conferences [67] P.Hazdra, J.Voves, E.Hulicius, J.Pangrác and Z.Šourek, Ultrathin InAs and modulated InGaAs layers in GaAs grown by MOVPE studied by photomodulated reflectance spectroscopy, Proc. of MRS meeting, Strasbourg 31.5. -3.6. 2005, p. P-18/32 [68] M.Fulem, K.Růžička, V.Růžička, T.Šimeček, E.Hulicius, J.Pangrác, Naphthalene as a Reference Material for Vapour Pressure Measurement, Thermodynamics 2005 6th-8th April 2005, Sesimbra, Portugal, Proc P. 12 [69] M.Fulem, K.Růžička, V.Růžička, T.Šimeček, E.Hulicius, J.Pangrác, Reliable extrapolation of vapour pressure data using simultaneous multi-property correlation for TMGa and TMAl, EW MOVPE XI, Lausane, June 6-8th 2005, Proc. p. 219-221 [70] A. Hospodková, V. Křápek, O. Bonaventurova, K. Kuldová, J. Pangrác, E. Hulicius, J. Oswald, T. Šimeček, Modification InAs/GaAs quantum dot shape in vertically correlated structures, EW MOVPE XI, Lausane, June 6-8th 2005, Proc. p. 87-89 [71] L. Dózsa, P. Hubik, A.L. Tóth, A. Pongrácz, E. Hulicius, A.A. Koós, Nanostrucure in In0.2Ga0.8As/GaAs quantum well structure, Hungarian Nanotechnolgy Symposium 2005, HUNS 2005, 21-22 March, 2005., Budapest, Hungary, ISBN 9637371176, Proc p. 52 [72] K.D. Moiseev, E.V. Ivanov, G.G. Zegrya, M.P. Mikhailova, Yu.P. Yakovlev, E. Hulicius, A. Hospodkova, J. Pangrac, K. Melichar, T. Simecek, Room-temperature electroluminiscence of InAsSbP/InAsSb/AlAsSb qauntum wells grown by MOVPE, presented at NGS-12, 2005, Toulouse, France [73] J. Cihelka, V. Horká, S. Civiš, T. Šimeček, E. Hulicius, J. Oswald, J. Pangrác, A. Vicet, Y. Rouillard, A. Salhi, C. Alibert, R. Werner, and J. Koeth, Laser diode photoacoustic spectroscopy near 2.3 μm, MIOMD VII conference, Lancaster 2005, Proc. p. 62 [74] K. Moiseev, K.D. Moiseev, E.V. Ivanov, G.G. Zegrya, M.P. Mikhailova, Yu.P. Yakovlev, E. Hulicius, A. Hospodkova, J. Pangrac, K. Melichar, T. Simecek, Electroluminescence AiSb/InAsSb/AlSb quantum well heterostructure grown by MOVPE, MIOMD VII conference, Lancaster 2005, Proc. p. 51 [75] L. Dózsa, P. Hubik, A.L. Tóth, A. Pongrácz, E. Hulicius, A.A. Koós, J. Oswald, NOrange-peel effect in InGaAs/GaAs anostrucure in In0.2Ga0.8As/GaAs quantum well structure, Hungarian Nanotechnolgy Symposium 2005, HUNS 2005, 21-22 March, 2005., Budapest, Hungary, ISBN 9637371192 ISBN 9637371184, Proc. p. 127-130 [76] F. Dubecky, [77] E. Hulicius, A. Hospodková, K. Kuldová, V. Křápek, J. Humlíček, J. Pangrác, J. Oswald, K. Melichar, and T. Šimeček, Characterization of MOVPE prepared InAs/GaAs quantum dots, accepted for Mezinárodní konference "Nanovědy, nanotechnologie a nanomateriály", NANO´05, 8. - 10. 11. 2005 , Brno, VUT, Fak. stroj. inž., Abstr. booklet p. 29 [78] K.Kuldová, J. Oswald, E. Hulicius, A. Hospodková, J. Pangrác, and K. Melichar, InAs/GaAs Quantum Dots with Long Wavelength Emission, accepted for Mezinárodní konference "Nanovědy, nanotechnologie a nanomateriály", NANO´05, 8. - 10. 11. 2005, Brno, VUT, Fak. stroj. inž., Abstr. booklet p. 104

==================================================== E Papers at the National Conferences [62] P.Hazdra, J,Voves, E.Hulicius, J.Pangrác, Ultrathin MOVPE Grown InAs Layers in GaAs Characterized by Photomodulated Reflectance Spectroscopy, Workshop 2005, Prague February 7-11, 2005 [63] J. Pangrác, J. Walachová, J. Vaniš, E. Hulicius, PROSTOROVĚ ROZLIŠENÁ BALISTICKÁ ELEKTRONOVÁ EMISNÍ SPEKTROSKOPIE BEES NA JEDNOTLIVÝCH KVANTOVÝCH TEČKÁCH InAs/GaAs UZAVŘENÝCH V AlGaAs/GaAs HETEROSTRUKTUŘE, NANOTEAM Kick-off meeting Brno, 21.4. 2005

MOVPE projects 2005/2006 EC Gas laser analysis by infrared spectr. (GLADIS)–Cost RTD IST-2001-35178 (2002-05) GAČR Kvantově rozměrné, napnuté polovodičové struktury připravené technologií MOVPE (garant postdoktorandského grantu - A Hospodková) 202/02/D069 (2002-2005) GAČR Kvantové tecky s dlouhovlnnou emisí (projekt J.Oswalda)-202/03/0413 (2003-05) GAAV Mechanismus zářivé rekombinace v subnanometrových InAs/GaAs laserových strukturách (spoluřešitel je FEL ČVUT) A1010318 (2003-2005) GAČR Měření tenze par organokovů (spoluřešitel prof. V. Růžičky)- 203/04/0484 (2004-06) EC Network of Excelence NoE - Photonic Integrated Components and Circuits (ePIX) (koordinátor pracoviště přidruženého partnera č. 10) - (2004-2009) GAČR Emise z kvantových teček (účast na projektu J.Pangráce)- 202/05/.... (2005-2007) GAČR GAČR

Kvantové tečky - příprava, PL, teorie Oswald/Munzar/Hazdra- 202/06/.... (2006-2008) Kvantové tečky – příprava, tvar, teorie, Krapek/Hospodková - 202/06/.... (2006-2007)

EU STREP MŠMT Centrum

NEMIS 2006-9 ?? (Evaluace - 25.5 bodu, (23 práh), ale …) CARDINAL 2006-10 ??

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

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 (Dianov – FIAN). Ternární a kvaternární sloučeniny na bázi Sb (FIAN (GIREMET), později FTI, Bel Lab., Kobayashi, …) - vše LPE Ale, … Jiné aplikace – viz úvod. Naše první práce: (můj první kontakt antimonidy a MIR lasery byl v letech 1976/77, ale, ..) V osmdesátých letech ve FTI Ioffe spolupráce již možná byla.

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


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

1500 0 -1500

T = 60 °C, I = 100-120 mA

1500 0

T = 60 °C, I = 83-103 mA

4334.5

4336.0

1500 0 -1500

4336.5

150

4337.0

T = 52.7 °C, I = 98-118 mA

4337.5

4338.0

T = 52.7 °C, I = 79-99 mA

4339.0

1500 0 -1500

4335.5

4338.5

4339.5

4339.0

4340.0

4340.5

T = 46.4 °C, I = 100-120 mA

4340.0

1500 0 -1500

T = 44.1 °C, I = 97-117 mA

4341.0

1500 0 -1500

4340.5

4341.5

4341.0

4342.0

4342.5

T = 44.1 °C, I = 78-98 mA

4343.0

4343.5

4344.0

EL Intensity [arb. units]

1500 0 -1500

4335.0

100

50

0 1000

Absorption measurement

CONDITIONS Ageing: TA=50 °C, IA=100 mA Measuring: TM=25 °C, IM=60 mA 2000

3000

4000

5000

Intensity (arb.u.)

Ageing time [hours] T = 40.7 °C, I = 86-106 mA

1500 0

4343.5

1500 0

4344.5

4345.0

1500 0 -1500

4344.5

4345.5

4346.0

T = 34.8 °C, I = 79-99 mA

4346.5

1500 0 -1500 1500 0 -1500

4344.0

T = 34.8 °C, I = 98-118 mA

4347.0

4347.5

4348.0

T = 34.8 °C, I = 60-80 mA

4348.0

4350.0 T = 22.2 °C, I = 79-99 mA

1500 0 -1500

3000 1500 0 -1500

4353.0

4348.5

4351.5

4349.0

T = 22.2 °C, I = 98-118 mA

4352.0

T = 22.2 °C, I = 60-80 mA

4353.5

4350.5

4349.5

4351.0

4352.5

4354.0

4353.0

4354.5

6000

3000

Methane Ethane x 10 Butane x 10

2500

Intensity(a.u.)

2000 1500 1000 500 0 -500 4210.0

4210.5

4211.0 -1

Wavenumber(cm )

4211.5

Growth and properties of InAs/InxGa1-xAs/GaAs quantum dot structures E. Hulicius1, J. Oswald1, J. Pangrác1, J. Vyskočil1,3, A. Hospodková1, K. Kuldová1, K. Melichar1, T. Šimeček1, T. Mates 1, V. Křápek 4, J.Humlíček 4, J. Walachová2, J. Vaniš2, P. Hazdra3, and M. Atef 3 MOVPE laboratory 1Institute 2Institute 3CTU 4MU

of Physics AS CR, v. v. i., Cukrovarnická 10, 162 00, Prague 6, Czech Republic

of Photonics and Electronics AS CR, v. v. i., Chaberská 57, 182 51 Prague 8, Czech Republic

- FEE, Technická 2, 166 27, Prague 6, Czech Republic

- PřF, Kotlářská 2, 611 37 Brno, Czech Republic

Vertically correlated structures

Lateral shape of InAs/GaAs quantum dots in vertically correlated structures We found ways to control the energy difference between PL transitions by adjusting properly the spacer thickness, the number of QD layers, and the growth conditions (e.g. V/III ratio). We also found an efficient way to control the emission wavelength by changing the number of QD layers.

A. Hospodková, E. Hulicius. J. Oswald, J. Pangrác, T. Mates, K. Kuldová, K. Melichar, and T. Šimeček, Properties of MOVPE InAs/GaAs quantum dots overgrown by InGaAs, J. Cryst. Growth, 298 (2007), 582-585.

Vertically correlated structures

Spacer thickness 1.6 b

1.4 circular Q D

a

1.0

Yellow = GaAs

[1 1 0 ]

2

4

6

8

S p acer thickne ss [n m ]

10

E

70

PL intensity [a.u.]

0.8

Energy difference [meV]

1.2

Blue = InAs

[-110]

QD elongation a/b

1.8

60

50

6 4 2 0 0.8

0.9

1.0

1.1

Energy [eV] 40

30

4

6

8

10

Spacer thickness [nm]

J. Cryst. Growth 298 (2007) 582-585.

Kvantové tečky

Magnetophotoluminescence, elongation

Elongation of InAs/GaAs QD determined from magnetophotoluminescence measurements

We use magnetophotoluminescence for determination of the lateral anisotropy of buried quantum dots. While the calculated shifts of the energies of higher radiative transitions in magnetic field are found to be sensitive to the lateral elongation, the shift of the lowest transition is determined mainly by the exciton effective mass. This behavior can be used for determining both the effective mass and the elongation fairly reliably from spectra displaying at least two resolved bands.

V. Křápek, K. Kuldová, J. Oswald, A. Hospodková, E. Hulicius, J. Humlíček, Elongation of InAs/GaAs quantum dots from magnetophotoluminescence measurements, Appl. Phys. Lett. 89 (2006) 153108.


Fig. 1 MPL energies calculated for a) circular and b), c) elongated QDs. Parameters used in the calculations: m* = 0:045m0, ħx = 100 meV, a) ħy = 100meV (L = 1:0), b) ħy = 150meV (L = 1:5), c) ħy = 200meV (L = 2:0). The energies of the lowest transition at zero field were set to 1.1 eV (corresponding to the vertical confinement energy). Appl. Phys. Lett. 89 (2006) 153108.


Fig. 2 Energy of the lowest MPL transition against magnetic field for elongated QDs. The experimental values (squares) and calculated energies with parameters ħx = 100 meV, ħy going from 100meV (thinner lines) to 200meV (thicker lines), and effective masses 0:03m0 (dashed), 0.04m0 (dotted), 0.05m0 (dash dotted), 0.06m0 (dash dot dotted), indicated by the arrows. The best agreement with the experimental data has been obtained for ħy = 160meV and m* = 0.045m0 (thick solid line). Appl. Phys. Lett. 89 (2006), 153108.


Fig. 3 Energy of the first higher MPL transition against magnetic field for elongated QDs. The experimental values (squares) and calculated energies with parameters ħx = 100 meV, m* going from 0.045m0 (thinner lines) to 0.05m0 (thicker lines), and ħy values of 100meV (dashed), 120meV (dotted), 140meV (dash dotted), 160meV (dash dot dotted), 180meV (short dashed), 200meV (short dotted). The best agreement with the experimental data has been obtained for ħy = 160meV and m* = 0.045m0 (thick solid line). Appl. Phys. Lett. 89 (2006), 153108.

BEEM / BEES

Study of InAs quantum dots in AlGaAs/GaAs heterostructure by

ballistic electron emission microscopy/spectroscopy

J. Walachová, J. Zelinka, V. Malina, J. Vaniš, F. Šroubek, J. Pangrác, K. Melichar, and E. Hulicius, Study of InAs quantum dots in AlGaAs/GaAs heterostructure by ballistic electron emission microscopy/spectroscopy, Appl. Phys. Lett. 91 (2007) 042110 and Appl. Phys. Lett. 92 1 (2008) 012101-1.

BEEM (microscopy)

AFM – topography

ballistic current (in pA at Itun = 2.5 nA, Vtun = 1.5 V)

BEES (spectroscopy), derivated from V-A characteristics of QD structure

Appl. Phys. Lett. 91 (2007) 042110.

Thank you for your attention

2015

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