Zhores Alferov The History of Semiconductor Heterostructures Reserch: from Early Double Heterostructure Concept to Modern Quantum Dot Structures

Transcription

1 Zhores Alferov The History of Semiconductor Heterostructures Reserch: from Early Double Heterostructure Concept to Modern Quantum Dot Structures St Petersburg Academic University Nanotechnology Research and Education Centre RAS

2 Introduction Transistor discovery Discovery of laser-maser principle and birth of optoelectronics Heterostructure early proposals Double heterostructure concept: classical, quantum well and superlattice heterostructure. God-made and Man-made crystals Heterostructure electronics Quantum dot heterostructures and development of quantum dot lasers Future trends in heterostructure technology Summary 2

3 The Nobel Prize in Physics 1956 "for their researches on semiconductors and their discovery of the transistor effect" William Bradford Shockley John Bardeen Walter Houser Brattain

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7 W. Shockley and A. Ioffe. Prague

8 The Nobel Prize in Physics 1964 "for fundamental work in the field of quantum electronics, which has led to the construction of oscillators and amplifiers based on the maser-laser principle" Charles Hard Townes b Nicolay Basov Aleksandr Prokhorov

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10 Proposals of semiconductor injection lasers N. Basov, O. Krochin and Yu. Popov (Lebedev Institute, USSR Academy of Sciences, Moscow) JETP, 40, 1879 (1961) M.G.A. Bernard and G. Duraffourg (Centre National d Etudes des Telecommunications, Issy-les-Moulineaux, Seine) Physica Status Solidi, 1, 699 (1961) 10

11 Lasers and LEDs on p n junctions January 1962: observations of superlumenscences in GaAs p-n junctions (Ioffe Institute, USSR). Sept.-Dec. 1962: laser action in GaAs and GaAsP p-n junctions (General Electric, IBM (USA); Lebedev Institute (USSR). Light intensity Wavelength Cleaved mirror p n + GaAs E n F Eg L p D L n D hν E p F Condition of optical gain: E n F E p F > E g 11

12 The Nobel Prize in Physics 2000 "for basic work on information and communication technology" for developing semiconductor heterostructures used in high-speed- and opto-electronics for his part in the invention of the integrated circuit Zhores I. Alferov b Herbert Kroemer b Jack S. Kilby

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14 circuit 14

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17 Fundamental physical phenomena in classical heterostructures (a) E c E c Electrons F n One-side Injection Propozal 1948 (W. Shokley) F p Experiment 1965 (Zh. Alferov et al.) E v Holes (b) Electrons Superinjection F n E c Theory 1966 (Zh. Alferov et al.) Holes F p E v Experiment 1968 (Zh. Alferov et al.) (c) Electrons Diffusion in built-in quasielectric field Theory 1956 (H. Kroemer) Experiment 1967 (Zh. Alferov et al.) 17

18 Fundamental physical phenomena in classical heterostructures (d) F n E c F p E v Electron and optical confinement Propozal 1963 (Zh. Alferov, R. Kazarinov) (H. Kroemer) Experiment 1968 (Zh. Alferov et al.) (e) E c E v Superlattices Theory 1962 (L.V. Keldysh) Experiment 1970 (L. Esaki et al.) Stimulated emission: Theory 1971 (R. Kazarinov and R. Suris) Experiment 1994 (F. Capasso et al.) 18

19 Heterojunctions a new kind of semiconductor materials: Long journey from infinite interface recombination to ideal heterojunction Energy gap (ev) [300 K] AlP GaP GaAs Ge InP GaSb AlSb InAs Lattice constant ( Å) [300 K] Lattice matched heterojunctions Ge GaAs 1959 (R. L. Anderson) AlGaAs 1967 (Zh. Alferov et al., J. M. Woodall & H. S. Rupprecht) Quaternary HS (InGaAsP & AlGaAsSb) Proposal 1970 (Zh. Alferov et al.) First experiment 1972 (Antipas et al.) 19

20 Radiation spectrum for the first low threshold Al x Ga 1 x As DHS laser at room temperature (3) 1.59 ev (a) Radiation intensity (arb. units) (2) 1.61 ev (1) ev 1.61 ev 1.39 ev 300 K 2 J th = 4300 A/cm (2) (1) (b) Wavelength ( Å) Wavelength ( Å) 20

21 Schematic representation of the DHS injection laser in the first CW-operation at room temperature Metal SiO 2 p + GaAs 3 µm p Al0.25Ga0.75As 3 µm p GaAs 0.5 µm p Al0.25Ga0.75As 3 µm n GaAs Metal Copper 250 µm 200 ma 120 µm 21

22 Heterostructure solar cells Space station Mir equipped with heterostructure solar cells 22

23 Heterostructure microelectronics Heterojunction Bipolar Transistor E c F E v E c E v Suggestion 1948 (W.Shockley) Theory 1957 (H.Kroemer) Experiment 1972 (Zh.Alferov et al.) AlGaAs HBT HEMT 1980 (T.Mimura et al.) E E c E 1 c F E v E 0 E v NAlGaAs-n GaAs Heterojunction Propagation delay 10 ns 1 ns 100 ps 10 ps J J 100 nw 1 µw 10 µw 100 µw 1 mw 10 mw Power dissipation Speed-power performances 23

24 Heterostructure Tree (by I. Hayashi, 1985) Wavelength Division Multiplexity All Optical Link Laser Disk Laser Printer Optical Sensor High Power Electronics Multi- Wavelength Phased LD Array LD Detector Array LD LED Wide Band Optical Transition APD PIN PIN-FET LD-Driver One Chip Repeater Monolithic OEIC Switch SSI Integration of Optical and Electronic Devices Integration of Optical Devices MSI Integration Technology Device Technology LSI Integration of Bifunctional Devices Advanced LAN Bidirectional Video Network Optical Connection Between LSIs Optical Wiring Inside LSI FET HBT HEMT Super High Speed Computer GaAs IC One Chip Computer HS Solar Cell's Substrate Crystal Epitaxi Thin Film Process Technology Material Characterization 24

25 Impact of dimensionality on density of states P N 3D P N P N 2D 1D L x L z L z Density of states E gap E 0 E 1 Energy E 00 E 01 P N 0D L x L z L y E 000 E

26 Temperature dependence of the normalized threshold current for different DHS lasers Normalized threshold current J th Jth( T) J th = T = exp J th (0) (d) (c) (b) (a) T 0 (a) T 0 = 104 C (b) T 0 = 285 C (c) T 0 = 481 C (d) = T Temperature ( C) (a) Bulk (b) Quantum well (c) Quantum wire (d) Quantum dot 26

27 Stranski Krastanow growth mode High surface energy of the substrate thin wetting layer High surface energy of the film 2D growth High strain energy of the film 3D Clusters Frank van der Merve Volmer Weber Stranski Krastanow 27

28 nm Cross-section of high resolution electron micrograph image of a single quantum dot for 3-ML InAs deposited; arrows indicate the boundary facets. 28

29 Cross-section TEM image of MBE-grown laser with InGaAs-AlGaAs QDs 20 nm 2 nm Al0.3Ga0.7As 1 nm GaAs 50 SL Al0.15Ga0.85As matrix T s = 480 C Vertically coupled quantum dots InGaAs 2 nm Al0.3Ga0.7As 1 nm GaAs 47 SL Cladding layers are grown at 700 C High power operation up to 1W CW 29

30 Vertical-Cavity Surface-Emitting Lasers Edge Emitting Laser Vertical Cavity Surface Emitting Laser (VCSEL) VCSELs: Ultralow threshold current High beam quality Monolitically-integrated mirrors Planar technology, on-wafer testing, dense arrays, on-chip integration 140% annual market growth. Need in reliable 1.3 & 1.55 µm VCSELs, in UV VCSELs 30

31 Quantum cascade lasers Band diagram Layer sequence Emission spectrum at room temperature Optical power (log., a.u.) Pulsed room temperature Wavelength, µm Voltage, V Light- and Volt-current characteristics 8K 150K 200K 250K Current, A Power, mw 31

32 Milestones of semiconductor lasers 10 5 J 2 th (A/cm ) A/cm2 (1970) 4.3 ka/cm2 (1968) Impact of Double Heterostructures 160 A/cm2 (1981) Impact of SPSL QW Impact of Quantum Wells 40 A/cm2 (1988) Impact of Quantum Dots 19 A/cm2 (2000) 6 A/cm2 (2002) Years Evolution and revolutionary changes Reduction of dimensionality results in improvements 32

33 Magic Leather energy consumption Energy Carrier Oil Gas Coal Nuclear Power (thermal reactors) Reserves (known and extractive) (GWatt year) Total throughout the world Consumption rate (GWatt) * Period of exhaust (years) Total Nuclear Power (fast reactors) * *Calculated value 33

34 The evolution of achieved in the world till 2006 and predicted efficiencies of solar cells based on III-V semiconductors 50 Efficiency (%) of solar energy conversion Concentrator AlGaAs/GaAs Singlejunction III-V Concentrator Multi-junction Thin-Film Si Cryst. Si one-sun Concentr. Si Year 34

35 Concentrator PV installations at the Ioffe Institute Mirrors, large cells, heat pipes (early 1980s) Fresnel lenses, medium cells (middle of 1980s) Smooth lenses, small cells (late 1980s) The tendency in concentrator PV: from large to small concentrators at high concentration ratio! 35

36 Multijunction solar cells provide conversion of the solar spectrum with higher efficiency. Achievable efficiency of multijunction cells is > 50% Ge Si GaInP GaAs Spectral irradiance (W/m µm) Wavelength (nm) Wavelength (nm)

37 The theoretical limit for MJ cells x 850 W/m² AM1,5d T = 333 K 70 Calculation made in the radiative limit Calculated for the concentration limit Optimum band gaps Efficiency (%) assumed Number of pn-junctions 37

38 Evolution of the solar electrical capacities till 2030 year Installed capacities (GW) USA Europe Japan World Year

39 Is Solar Energy Conversion an Option to Solve the Energy Problems in Future? Yes! 39

40 White light-emitting diodes: efficiency, controllability, reliability, life time Today: InGaN-QW/GaN/sapphire light-emitting chip + YAG Ce phosphor Outlook: Monolithic microcavity LED with InGN/GN MQW active region White Phosphor YAG Ce White Sapphire Sapphire Buffer Buffer n+gan n+gan InGaN-QW Ti/Ag/Au p+gan InGaN-QW p+gan Ni/Ag/Au Ti/Ag/Au Bragg resonator GaN/AlGaN Ni/Ag/Au + simple design phosphor loss + monolithic nature + absence of additional loss 40

41 Nanostructures for high power semiconductor lasers Solid-state lasers pumping Fibre lasers Atmospheric and fibre optical communication Medical apparatus Atmospheric lidars Thickness, nm 5 nm Band gap, ev Navigation Energy transport in the atmosphere and fibre Laser efficiency > 75% Laser power > 10 W Welding and cutting Laser array output power > 100 W Matrix output power > 5 kw 41

42 Summary 1. Heterostructures a new kind of semiconductor materials: expensive, complicated chemically & technologically but most efficient 2. Modern optoelectronics is based on heterostructure applications DHS laser key device of the modern optoelectronics HS PD the most efficient & high speed photo diode OEIC only solve problem of high information density of optical communication system 3. Future high speed microelectronics will mostly use heterostructures 4. High temperature, high speed power electronics a new broad field of heterostructure applications 5. Heterostructures in solar energy conversion: the most expensive photocells and the cheapest solar electricity producer 6. In the 21st century heterostructures in electronics will reserve only 1% for homojunctions 42