innovation and development of study field nanomaterials at

These materials have been developed within the ESF project: Innovation and development of study field Nanomaterials at the Technical University of Liberec

Innovation and Development of Study Field Nanomaterials at the Technical University of Liberec

nano.tul.cz

http://nano.tul.cz/projekt-esf-na-podporu-oboru-nanomaterialy

Studijní program:NanotechnologieStudijní obor: Nanomateriály

(organizuje prof. J. Šedlbauer, FPP TU v Liberci)

Preparation of semiconductor nanomaterials

(koordinuje prof. E. Hulicius, FZÚ AV ČR, v.v.i.)

9. a 10. Semiconductor (nano)hetero-structures and devices.Semiconductor heterostructures, exploitation of quantum-size

properties of nanostructures, reasons of implementation, materials.Understanding of specifics of quantum-size structures and devices will

be important for students pretending for better classification.Specifics of quantum-size device properties will be subject of

questions.

Semiconductor heterostructures, using of quantum-size properties

of nanostructures, reasons of implementation, materials,

future improvementsSemiconductors, monocrystals – not only, but mainly

Why does crystal exist? Crystal lattice and properties (electrical, optical, (mechanical – not here))

Role of defects? Types of defects, their concentration, influence on devices.

(point defects, dislocations, stacking faults, twins, ...)

Crystal systemkrystalová soustava

Minimal symmetryminimální symetrie

Triclinicaltriklinická (trojklonná)

Nožádná

Monoclinicalmonoklinická (jednoklonná)

One double foliate axe along cjedna 2četná osa podél c

Orthorhombicortorombická(rombická, kosočtverečná)

Three double foliate axes along a, b, ctři 2četné osy podél a, b , c

Tetragonaltetragonální (čtverečná)

One four foliate axe along cjedna 4četná osa podél c

Cubic

kubická (izometrická)

Four triple foliate axes along cube body diagonalčtyři 3četné osy podéltělesových úhlopříček krychle

Hexagonalhexagonální (šesterečná)

One six foliate axe along cjedna 6četná osa podél c

Trigonaltrigonální(romboedrická, klencová)

One triple foliate axe along axe of hexagonal celljedna 3četná osa podél osy hexagonalní buňky

Bravais latticesIt is possible to prove that only 14 differentBravais space lattices does exist. See table:

Crystal lattice, electron and hole band energy structure

„High-school band structure“, bands in „k“-space, (Brillouinzone, direct and indirect semiconductors, p-n junction,heterostructure, quantum well, density of electron states).

Band structure of Si and GaAs

Crystal lattice, electron and hole band energy structurer

„High-school band structure“, bands in „k“-space, (Brillouinzone, direct and indirect semiconductors, p-n junction,heterostructure, quantum well, density of electron states).

State exam questions at FEL-CVUT:

Jevy v polovodičích: Pásová struktura polovodičů, hustota stavů, efektivní hmotnost, přímý a nepřímý polovodič. Statistika elektronů a děr ve vodivostním a valenčním pásu, Fermiho hladina, vliv příměsí. Poissonova rovnice, rovnice kontinuity, difúzní a vodivostní proud, pohyblivost. Boltzmanovakinetická rovnice, rozptylové mechanismy. Generační a rckombinační mechanismy, doba života, difúnírovnice.Přechod p-n: oblast prostorového náboje, rozložení koncentrace nositelů náboje, intenzity elektrického pole, potenciálu, difúzní napětí, Shockleyho rovnice VA charakteristiky, injekce a extrakce nositelů náboje, injekční účinnost. Bariérová a difúzní kapacita. Průraz tunelový, lavinový, jejich teplotní závislost.Heteropřechody, rozměrové kvantování, elektron v kvantové jámě, hustota stavů v 2D, 1D a OD polovodiči, rezonanční tunelování, transport elektronů v supermřížce.Dioda, výkonová dioda PIN, varikap, Zenerova dioda, tunelová dioda.Kontakt kov-polovodič - kvalitativní popis dějů v: usměrňující a neusměrňující kontakt, VA charaktcristika, Schottkyho dioda. Propustné a závěrné vlastnosti, porovnání s pn přechodem. Teplotnívlastnosti.Struktura MIS - kvalitativní popis dějů ve: slabá a silná inverze, pásový modely, reálná struktura MIS, vliv náboje v oxidu a na rozhraní.Bipolární tranzistor: funkce, zbytkové proudy, průrazné napětí, charakteristiky, zapojení SB, SC, SE a jejich vlastnosti, ss pracovní bod a jeho nastavení, parametry h a y, náhradní obvody, kmitočtové a teplotnívlastnosti. Spínací aplikace. Vliv povahy zátěže, první a druhý průraz.Unipolární tranzistor: JFET. MESFET, MOSFET, DMOS. Indukovaný a zabudovaný kanál. Vlastnosti, charakteristiky, parametry. Základní zapojení, ss pracovní bod a jeho nastavení, parametry, kmitočtové a teplotní vlastnosti. Jevy krátkého kanálu MOSFET.

Principles of electronic devices

Vícevrstvé součástky: diak, tyristor, charakteristiky a parametry. GTO.Optoelektronické součástky: Fotoelektrický jev, fotovodivost, spontánní a stimulovaná emise, absorpce.elektroluminiscence, katodoluminiscence.Optické vláknové a planární vlnovody: princip funkce, materiálově-technologické řešení, základnívlastnosti. Polovodičové zdroje záření a detektory: princip funkce, materiálové a konstrukční řešení, základní vlastnosti a parametry. Optické přenosové systémy: základní principy, konstrukční komponenty, dosahované parametry. Optické vláknové senzory: základní principy, vlastnosti.Vysokofrekvenční a kvantově vázané polovodičové součástky - principy činnosti, aplikace: RTD, MESFET, HEMT - modulační dotace, HBT, HET - překmitový jev, jednoelektronový tranzistor-Coulombovská blokáda, laser s kvantovou jámou, polovodičový fotonásobič.Šum (typy, š. pasivní součástky, přechodu PN, FET, BJT).Modely součástek – statický, pro malý, velký signál, nf., vf. včetně základních modelů používaných v simulačních programech.Trendy technologie submikronových integrovaných obvodů na křemíku, pokroky ve zvyšování hustoty, integrace – ULSI, GSI. Ultrafialová , rentgenová , elektronová , iontová litografie. Konstrukcesubmikronového tranzistoru - potlačení jevu krátkého kanálu a horkých elektronů. Technologie propojovánía víceúrovňové metalizace. Multičipové moduly. Jazyky HDL. Prostředky syntézy: simulace a verifikace návrhu IO.Pasivní součástky diskrétní a integrované. Základní konstrukce a parametry. Frekvenční a teplotnívlastnosti.Mikrosystém, mikrosenzor a mikroaktuátor - charakteristické vlastnosti (citlivost, nelinearita, atd.), principy činnosti (elektrostatické, piezoelektrické, magnetické, tepelné, optické, mechanické. atd.).

Suitable and used elements, compounds and materials

Elementary semiconductors:silicon, silicon, silicon, (also germanium, selenium, diamond), but ...They have indirect junctions, forbidden gap (Eg) and refraction index (n) is changeable only small.

Compounds semiconductors:AIIIBV - GaAs, InP, GaSb, ...AIIBVI - CdTe, CdSe, ...AIVBIV - GeSi, …AX

IIIB(1-X)IIICV - AlGaAs, …

AXIIIB(1-X)

IIICYVD(1-Y)

V - GaInAsSb, …

Elements and compounds

Compound semiconductors

II.B III.A IV.A V.A VI.A

2 B C N O

3 Al Si P S

4 Zn Ga Ge As Se

5 Cd In Sn Sb Te

6 Hg Tl Pb Bi Po

Dependence of Eg and absorption edge on the lattice constant:

Forbidden gap dependence on lattice constant for some other materials

Repetition general information about:

Band structure:

If you are familiar with this subject, you can jump over.

Creation of band structure

Band structure in k-space:

První aproximace poruchového počtu, bez započtení spin-orbitální interakce

První aproximace poruchového počtu, se započtením spin-orbitální interakce

Druhá aproximace poruchovéhpočtu, se započtením spin-orbitální interakce

Structures, heterostructures, nanostructures and peculiarities (material engineering)

Homogenous structures

P-N junctions:Electronics is based on them. Few interesting, simple, cheap, efficient device examples:

- LEDs based on GaAs:Si amphoteric doping;- semiconductor solar cells (mainly Si);

Semiinsulating on highly conductive layer and vice versa.

Bulk crystal – separation layer (epitaxial buffer) – function epitaxial layer- (gradual improving crystallographic quality)

Monocrystal - polycrystalline – amorphous layer or vice versa.

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.).ObrStrained junctions.Obr


Not only heterostructures 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!!

Junctions type I., II. (a III.).ObrStrained junctions.Obr

Heterojunctions:(a) = b – the first type

(b) = a – the second type

(c) - the thirt type

Examples of the first type heterostructures can be different


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!!

Junctions type I., II. (a III.).

Strained junctions.Obr

Strained

and

relaxed

lattice

Quantum- size structures – Nano(hetero)structures -„quantum"

Decreasing of one or more dimension spaces in the structure to the level comparable with wavelength of electron (from tenths (0.1s) to tens (10s) nanometres (nm))

Quantum wellsQuantum wiresQuantum dots

Figs

We can create new „artificial“ types of band structures - superlattices(explanation difference between superlattice and multiple quantum well), quantum cascade lasers.

Density of electron energy states

„Peculiarities"

- Solving of troubles of Type II heterojunctions- QD InAs in GaAs on Si- Fullerenes (also buckyballs – C60, 90, 80

(According architect R. Buckminstera Fullera who proposed and created similar dome buildings.)

- Quantum cascade lasers- Nanocoils- Spinotronics

„Peculiarities"

- Solving of troubles of Type II heterojunctions- QD InAs in GaAs on Si- Fullerenes (also buckyballs – C60, 90, 80)



QD InAs/GaAs na Si

„Peculiarities"




Základní způsoby generace záření ve (střední) infračervené oblasti

Conduction band schematic of GaInAs/ AlInAsquantum cascade laser lattice matched to InP.

Cross sectional schematic of laserwaveguide 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.

Tunable Emission Over a Wide Spectral Range

M. Razeghi, Center for Quantum Devices, Northwestern Univ., EvanstonUncooled 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 themost exciting projects at the Center for Quantum Devices (CQD) is uncooled infrared quantum cascade lasers (QCLs), which, being asemiconductor laser, is inherently compact and will help eliminate the need for bulky and unreliable cryogenic cooling. This translates to asmaller, 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.

Distributed Feedback (DFB) Quantum Cascade Lasers

High Performance Lasers Operating at Room Temperature

75 period waveguide coreCavity: 3 mm x 25 m

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.

Cross section image of a Au electroplatedQCL.

Cross section image of aburied-ridge QCL laser.

Highest average power QCL.

Comparison of groups >4 m

M. Razeghi, Center for Quantum Devices, Northwestern Univ., EvanstonUncooled 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 themost exciting projects at the Center for Quantum Devices (CQD) is uncooled infrared quantum cascade lasers (QCLs), which, being asemiconductor laser, is inherently compact and will help eliminate the need for bulky and unreliable cryogenic cooling. This translates to asmaller, 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.

„Peculiarities"




Using a combination of different materials to prepare useful functional devices (transistors, LEDs and lasers, detectors and photovoltaic cells, ...) with better parameters.It is possible to prepare new materials desirable properties like complicated ternaries or quaternaries non existing in the nature. It is possible to use combination of thin binaries instead of „chemistry“ of non existing ternaries with better properties.We can construct structures and devices (mainly on nanostructurebase) with new properties (superlattices, quantum cascade lasers (QCL), molecular electronics, nanorobots, devices with quantum wells, wires, dots, with photonic crystals, with photo-electro-chemical cells, etc).

(In this lectures there were not described nonsemiconductor structures, biological nanostructures, Au, Ag, Fe, TiO, ZnO nanoparticles with huge application fields, nanofibres, nanomechanics, nanocolours, nanotextile also with great application potential.)

Structures for devices based on nonclasical(nonintuitive) quantum physical effects

Examples of nano-hetero-structures andheterodimensional structures for later described devices.

HeterodimensionalDevice TechnologiesInterfaces between different-dimensional structures.

Examples of devices based on nonclasical(nonintuitive) quantum physical effects

May be the oldest one is tunnel diode.It is based on resonant tunnelling.Obr.HEMT transistors and other, e.g. one electron transistors.Obr.Quantum etalon of resistivity (ohm normal) is based on quantum Hall effect.Project MÚ, FEL a FZÚ (P. Svoboda)Semiconductor lasers and LEDs in general (and with QW and QD especially).Next lecture on gradual and abrupt improving of their parameters whennanostructures are used.

Kvantový normál odporu

Quantum etalon of resistivity(ohm normal)

Quantum normal of resistivity (ohm unit)

Examples of devices based on nonclasical(nonintuitive) quantum physical effects

May be the oldest one is tunnel diode.It is based on resonant tunnelling.Obr.HEMT transistors and other, e.g. one electron transistors.Obr.Quantum etalon of resistivity (ohm normal) is based on quantum Hall effect.Project MÚ, FEL a FZÚ (P. Svoboda)Semiconductor lasers and LEDs in general (and with QW and QD especially).Next lecture on gradual and abrupt improving of their parameters when nanostructures are used.

Thank you for your attention

Next:

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).

LDLaser 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.

ResumeLED relatively cheap, efficient, notdegrading light sourcesFurther 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, …

innovation and development of study field nanomaterials at

Documents