Preparation of semiconductor nanomaterials 2014/2015

Transkript

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

2 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.

3 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) later) mid-infrared (will be described in detail

4 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 ) = / m Wavelength ( m) Energy (ev) Frequency (THz) Wavenumber (cm -1 ) Visible Near Infrared (NIR) Mid Infrared (MIR) Far Infrared (FIR or THz) mm Wave > < < <10

5 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)

6 Examples of optoelectronic applications in the visible region

7 Examples of optoelectronic applications in the visible region

8 Examples of optoelectronic applications in the visible region

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13 Industrial MOVPE technology

14 Industrial MOVPE technology

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18 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. Adjucent spectral fields ultraviolet (nitrides, ZnO, diamond,...? many interesting applications) mid-infrared (will be described in detail later)

19 Mid-infrared region of the electromagnetic radiation is usually defined from 2do20μm. 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, )

20 Forbidden gap dependence on lattice constant for some semiconductor materials

21 In 1-x Ga x As y P 1-y Equation for parameters in general of quaternary semiconductors ( = linear combination of parameters of binar compounds): p(x,y) = (1-x)(1-y)p InP + (1-x)yp InAs + xyp GaAs + x(1-y)p GaP a(x,y) = x y xy Relation for forbidden gap of the quaternary semiconductors: E g (x,y) = x y x y xy x 2 y xy x 2 y 2

22 . Dependence of energy of forbidden gap on compound composition

23 Some of older IR materials:

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25 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;

26 LED Light Emitting Diode

27 1907(!) The first electroluminescent diode - SiC, H.J. Round (c) (Rediscovered by Losevem at 1928) Destriau - LEDs from ZnS Welker introduction of A III B V (GaAs) Lasers (RCA, GE, IBM, MIT) th- Expansion of epitaxial technologies th Implementation of heterostructures and quantum wells Solving of the laser degradation and diodes (dislocation free substrates).

28 Recombination and biases

29 Electroluminescent materials

30 Heterojunctions other point of view

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

32 LED structure with triple quantum well and electron blocking layer

33 Emmisson spektrum of LED?

34 The main problem of LEDs is a light exit!!

35 How to solve it??

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

37 ?... It is transparent, but

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

39 And external efficiency will be improved.?

40 And what about contacts...

41 ... Also its geometry is important.

42 Sometimes there are troubles with absorbed substrate.?

43 Antireflex covering improve efficiency and also lifetime.

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

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

46 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.

47 Improving of LEDs in time:

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

49 White diodes.

50 Two-colour diodes (in one chip!)

51 Also LEDs can work with resonator.

52 What is a cost of one lumen?

53 Spectral sensitivity of eye and LEDs properties.

54 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).

55 Laser jako prvek se zpětnou vazbou. Pásová struktura jednoduchý p-n přechod, injekce elektronů. Laserový čip hetrorostruktura, vlnovod, rezonátor. Vlnovod.

56 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

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58 Pásová struktura a index lomu. Proužková geometrie a vlnovod. Tvar výstupního optického svazku.

59 Types of the laser resonators:

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

61 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).

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

63 Due to heterojunctions can be created a waveguide:

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

65 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: and in equilibrium (d/dt = 0) is dn/dt = J/ed n/τ 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)

66 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

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

68 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.

69 Cooperation with FEL ČVUT a FZÚ AV ČR: Optical Power [a.u.] InAs layers S L ~7.9 nm 25 C 30 C 40 C 50 C 60 C 70 C 80 C 90 C 100 C Current Threshold Density [A/cm 2 ] Ls T 0 ~ 90 K T 0 ~ 160 K 0,5 0,4 0,3 0,2 0,1 Differential Quantum Efficiency 0,0 0,2 0,4 0,6 0,8 1,0 Current density [ka cm -2 ] The temperature variations of the dependence of laser optical output power on excitation current density for lascer with 7 InAs layers and thickness of S L ~7.9 nm. 10 0, Temperature [K] Temperature dependence of threshold current density and differential quantum efficiency for laser with 5 InAs layers.

70 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)

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

72 Strain in the structures can influence a threshold current.

73 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,

74 Thank you for your attention

75 Appendix Our results in this field

76 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)

77 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)

78 Srovnání laserů s ternární a supermřížkovou (MQW) aktivní oblastí Ternární InGaAs QW laser InAs/GaAs laser se supermřížkou Optical Power [a.u.] Intensity EL I ex =2 A I ex =2.25 A I ex =2.5 A I ex =3 A T=300 K 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] Intensity PL EL I ex =0.46A T=300K Emission Energy [ev] T 0 = 126 K laser B 25 C 35 C 45 C 55 C 65 C 75 C 85 C Current Density [A/cm 2 ] Current Density [A/cm 2 ]

79 Vlastnosti laserů s MQW v aktivní oblasti

80 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)

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82 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)

83 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

84 Proč jsou KT tak intenzivně studovány? KJ KT Hustota stavů v objemovém polovodiči, kvantové jámě a kvantové tečce (E) 3D 2D 0D E 1 E 2 E 3 E 4 E

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

86 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)

87 Zdroj:

88 TEM AFM 7 vrstev KT, oddělovací vrstvy 7.5 nm 3 vrstvy KT, oddělovací vrstvy 3.7 nm

89 3 QD TEM 7 QD 7 QW

90 Kvantové tečky

91 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 o C 2. GaAs podklad. vrstva 650 o C 1. GaAs substrát GaAs vrstvy: Prekursory TMGa a AsH 3, celk. tlak 70 hpa, celk. průtok 8 l/min, teplota 650 o C a 500 o C, poměr V/III 150 a 43. InAs vrstvy: 50 ml/min H 2 /TMIn, poměr V/III 85, čas růstu 9 s, přerušení růstu 30 s.

92 KT překryté InGaAs Původní KT KT překrytá GaAs KT překrytá InGaAs

93 Dosažená vlnová délka FL InAs/InGaAs KT

94 FL InAs/GaAs KT překrytých InGaAs InGaAs 23% In I PL (arb.u.) E PL (ev) 1508B bez ternaru 1524B 13%In I* B 23%In 1526B 6%In I*35 InAs GaAs Základní stav: 0.86 ev 1.44 m 1. excitovaný stav: 0.93 ev 1.3 m

95 AFM picture of InAs/GaAs QDs

96 GaAs: buffer 230 nm AlGaAs-n typ 570 nm AlGaAs 400 nm GaAs 150 nm GaAs 150 nm AlGa As 320 nm AlGaAs-p typ 570 nm GaAs 700 nm GaAs:Te substrate SPSLS 12x (InAs / GaAs)

97 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.

98 Naše výsledky a výstupy

99 MOVPE laboratory co-operations in ) 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)

100 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) ) 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 ) 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) ) 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) ) 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) 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

101 Current results 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 , 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 th-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 [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 [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, March, 2005., Budapest, Hungary, ISBN , 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, March, 2005., Budapest, Hungary, ISBN ISBN , Proc. p [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, , 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, , 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,

102 MOVPE projects 2005/2006 EC Gas laser analysis by infrared spectr. (GLADIS) Cost RTD IST ( ) GAČR Kvantově rozměrné, napnuté polovodičové struktury připravené technologií MOVPE (garant postdoktorandského grantu - A Hospodková) 202/02/D069 ( ) GAČR Kvantové tecky s dlouhovlnnou emisí (projekt J.Oswalda)-202/03/0413 ( ) GAAV Mechanismus zářivé rekombinace v subnanometrových InAs/GaAs laserových strukturách (spoluřešitel je FEL ČVUT) A ( ) GAČR Měření tenze par organokovů (spoluřešitel prof. V. Růžičky)- 203/04/0484 ( ) EC Network of Excelence NoE - Photonic Integrated Components and Circuits (epix) - (koordinátor pracoviště přidruženého partnera č. 10) - ( ) GAČR Emise z kvantových teček (účast na projektu J.Pangráce)- 202/05/... ( ) GAČR Kvantové tečky - příprava, PL, teorie Oswald/Munzar/Hazdra- 202/06/... ( ) GAČR Kvantové tečky příprava, tvar, teorie, Krapek/Hospodková - 202/06/... ( ) EU STREP NEMIS ?? (Evaluace bodu, (23 práh), ale ) MŠMT Centrum CARDINAL ??

103 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 * (COP 813) ( ) 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-CT ( ) EPICHEM, Bramborough, UK, AIXTRON, Aachen, Germany, RWTH, Aachen, Germany, UM2 University of Montpellier, France Gas Laser Analysis by Infra-red Spectroscopy (GLADIS) IST ( ) 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

104 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.

105 The NEMIS project aims at the development and realisation of compact and packaged vertical-cavity surface-emitting semiconductor laser diodes (VCSEL) for the 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

106

107 Optical Power [a.u.] C 50 C Excitation Current [ma] 0-10 EL Intensity [db] T=25 C T=50 C T=70 C I ex =70 ma Wavelength [nm]

108 Intensity (arb.u.) T = 60 C, I = ma T = 60 C, I = ma T = 52.7 C, I = ma T = 52.7 C, I = ma T = 46.4 C, I = ma T = 44.1 C, I = ma T = 44.1 C, I = ma T = 34.8 C, I = ma T = 34.8 C, I = ma T = 22.2 C, I = ma T = 22.2 C, I = ma T = 40.7 C, I = ma T = 34.8 C, I = ma T = 22.2 C, I = ma EL Intensity [arb. units] Absorption measurement CONDITIONS Ageing: T A =50 C, I A =100 ma Measuring: T M =25 C, I M =60 ma Ageing time [hours]

109 Methane Ethane x 10 Butane x 10 Intensity(a.u.) Wavenumber(cm -1 )

110 Growth and properties of InAs/In x Ga 1-x As/GaAs quantum dot structures E. Hulicius 1, J. Oswald 1, J. Pangrác 1, J. Vyskočil 1,3, A. Hospodková 1, K. Kuldová 1, K. Melichar 1, T. Šimeček 1, T. Mates 1, V. Křápek 4, J.Humlíček 4, J. Walachová 2, J. Vaniš 2, P. Hazdra 3, and M. Atef 3 MOVPE laboratory 1 Institute of Physics AS CR, v. v. i., Cukrovarnická 10, , Prague 6, Czech Republic 2 Institute of Photonics and Electronics AS CR, v. v. i., Chaberská 57, Prague 8, Czech Republic 3 CTU - FEE, Technická 2, , Prague 6, Czech Republic 4 MU - PřF, Kotlářská 2, Brno, Czech Republic

111 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),

112 Spacer thickness Vertically correlated structures 1.8 QD elongation a/b circular QD [-110] b [110] a Blue = InAs Yellow = GaAs Spacer thickness [nm] Energy difference [mev] 70 E PL intensity [a.u.] Energy [ev] Spacer thickness [nm] J. Cryst. Growth 298 (2007)

113 Kvantové tečky

114 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)

115 Magnetophotoluminescence, elongation Fig. 1 MPL energies calculated for a) circular and b), c) elongated QDs. Parameters used in the calculations: m* = 0:045m 0, 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)

116 Magnetophotoluminescence, elongation 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 0:03m 0 (dashed), 0.04m 0 (dotted), 0.05m 0 (dash dotted), 0.06m 0 (dash dot dotted), indicated by the arrows. The best agreement with the experimental data has been obtained for ħ y = 160meV and m* = 0.045m 0 (thick solid line). Appl. Phys. Lett. 89 (2006),

117 Magnetophotoluminescence, elongation 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 0.045m 0 (thinner lines) to 0.05m 0 (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* = 0.045m 0 (thick solid line). Appl. Phys. Lett. 89 (2006),

118 Study of InAs quantum dots in AlGaAs/GaAs heterostructure by ballistic electron emission microscopy/spectroscopy BEEM / BEES 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) and Appl. Phys. Lett (2008)

119 BEEM (microscopy) AFM topography ballistic current (in pa at Itun = 2.5 na, V tun = 1.5 V)

120 BEES (spectroscopy), derivated from V-A characteristics of QD structure Appl. Phys. Lett. 91 (2007)

121 Thank you for your attention