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1
Content available Numerical analysis of the compositional graded quaternary barrier AlGaN-based ultraviolet-C light-emitting diode
Malik S., Usman Muhammad, Hussain M., Munsif M., Khan S., Rasheed S., Ali S.
Opto-Electronics Review
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2021
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Vol. 29, No. 3
80--84
EN
The compositional graded quaternary barriers (GQBs) instead of ternary/conventional quantum barriers (QBs) have been used to numerically enhance the efficiency of AlGaN-based ultraviolet light-emitting diode (LED). The performance of LED with GQBs is examined through carrier concentrations, energy band diagrams, radiative recombination, electron and hole flux, internal quantum efficiency (IQE), and emission spectrum. As a function of the operating current density, a considerable reduction in efficiency droop is observed in the device with composition-graded quaternary barriers as compared to the conventional structure. The efficiency droop in case of a conventional LED is ~77% which decreased to ~33% in case of the proposed structure. Moreover, the concentration of electrons and holes across the active region in case of the proposed structure is increased to ~156% and ~44%, respectively.
2
Content available remote Optymalizacja obszaru aktywnego międzypasmowego lasera kaskadowego
Ryczko K.
Przegląd Elektrotechniczny
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2017
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R. 93, nr 8
24--26
PL
W tym artykule przedstawiono teoretyczne badania struktury pasmowej studni kwantowych II rodzaju InAs/GaInSb i InAs/GaAsSb, które mogą być stosowane jako obszary aktywne międzypasmowych laserów kaskadowych, emitujących w szerokim zakresie średniej podczerwieni. Stosując wielopasmowy model kp obliczono zależność energii oraz siły oscylatora fundamentalnego przejścia optycznego od grubości warstw stanowiących studnie kwantowe dla elektronu.
XX
In this paper, we present theoretical investigations of the band structure of type-II InAs/GaInSb and InAs/GaAsSb quantum wells dedicated for the active region of interband cascade lasers emitting in a broad range of mid infrared. We utilize the multiband kp theory in order to calculate the dependence of the energy and oscillator strength of the fundamental optical transition on the thickness of particular layers confining electrons.
3
Content available remote Influence of doping on the performance of GaAs/AlGaAs QWIP for long wavelength applications
Billaha A., Das M. K.
Opto-Electronics Review
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2016
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Vol. 24, No. 1
25--33
EN
Effect of doping and other device parameters on inter sub−band transition in the well, responsivity and dark current of GaAs/AlxGa1-xAs quantum well infrared photodetector (QWIP) is investigated using theoretical model. 2X2 Hamiltonian method is used to calculate Eigen energy states in this modelling. Results show that peak absorption, responsivity and spectral broadening width increase nonlinearly with increasing doping concentration in the well. Peak absorption coefficient increases with increase in well width also. Moreover, with increase in mole fraction of Al in AlxGa1-xAs barrier, the inter sub-band absorption is enhanced but, peak wavelength of absorption shifts towards shorter wavelengths. Dark current density depends on both, the doping concentration and applied bias.
4
Struktury kwantowe ZnMgO/ZnO/ZnMgO wykonywane metodą MBE
Kozanecki A., Sajkowski J., Stachowicz M., Przeździecka E., Syperek M.
Elektronika : konstrukcje, technologie, zastosowania
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2014
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Vol. 55, nr 9
13-15
PL
Tlenek cynku i struktury kwantowe ZnMgO/ZnO/ZnMgO uważane są za bardzo obiecujące materiały do zastosowań optoelektronicznych, ze względu na wartość przerwy energetycznej Eg > 3,3 eV i energię wiązania ekscytonu >60 meV. W tej pracy przedstawione zostaną wyniki naszych badań pojedyńczych studni (QW) i wielostudni kwantowych ZnMgO/ZnO/ZnMgO, otrzymywanych metodą epitaksji z wiązek molekularnych na różnych podłożach takich jak szafir. Zaprezentowane zostaną właściwości optyczne układów podwójnych studni kwantowych otrzymanych na podłożach szafirowych. Przedyskutowane zostaną mechanizmy oddziaływania między studniami, w szczególności zostanie pokazany wpływ sprzężenia między studniami na emisję ekscytonową.
EN
Zinc oxide is considered as a very attractive semiconductor for applications in optoelectronics, because of its wide band gap, Eg, of 3.3 eV and large exciton binding energy of 60 meV. ZnMgO alloy has been considered as a suitable material for the barrier layers in ZnMgO/ZnO/ZnMgO superlattice structures, because alloying of ZnO with MgO (Eg~7.7 eV) enables widening of the bandgap of ZnO up to at least 4.5 eV without loss of crystalline quality. In ZnMgO/ZnO/ZnMgO quantum wells the binding energy of excitons increases up to 100 meV which promises obtaining of efficient electroluminescence in devices operating on excitonic transitions at room temperature. In this presentation the results of our studies of single and multiple quantum well structures of ZnMgO/ZnO/ZnMgO grown by MBE on different sapphire will be presented. Optical properties of asymmetric coupled quantum wells grown on crystalline ZnO and on sapphire will be discussed. In particular, the influence of interwell coupling on the excitonic emission will be shown.
5
Content available remote Contactless electroreflectance spectroscopy of optical transitions in low dimensional semiconductor structures
Misiewicz J., Kudrawiec R.
Opto-Electronics Review
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2012
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Vol. 20, No. 2
101-119
EN
The authors present the application of contactless electroreflectance (CER) spectroscopy to study optical transitions in low dimensional semiconductor structures including quantum wells (QWs), step-like QWs, quantum dots (QDs), quantum dashes (QDashes), QDs and QDashes embedded in a QW, and QDashes coupled with a QW. For QWs optical transitions between the ground and excited states as well as optical transitions in QW barriers and step-like barriers have been clearly observed in CER spectra. Energies of these transitions have been compared with theoretical calculations and in this way the band structure has been determined for the investigated QWs. For QD and QDash structures optical transitions in QDs and QDashes as well as optical transitions in the wetting layer have been identified. For QDs and QDashes surrounded by a QW, in addition to energies of QD and QDash transitions, energies of optical transitions in the surrounded QW have been measured and the band structure has been determined for the surrounded QW. Finally some differences, which can be observed in CER and photoreflectance spectra, have been presented and discussed for selected QW and QD structures.
6
Content available remote Study of MOCVD growth of InGaAsSb/AlGaAsSb/GaSb heterostructures using two different aluminium precursors TMAl and DMEAAl
Wesołowski M., Strupiński W., Motyka M., Sęk G., Dumiszewska E., Caban P., Jasik A., Wójcik A., Pierściński K., Pierścińska D.
Opto-Electronics Review
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2011
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Vol. 19, No. 2
140-144
EN
The antimonide laser heterostructures growth technology using MBE epitaxy is currently well-developed, while MOVPE method is still being improved. It is known that the principal problem for MOVPE is the oxygen and carbon contamination of aluminium containing waveguides and claddings. The solution would be to apply a proper aluminium precursor. In this study we present the results of metal-organic epitaxy of In- and Al-containing layers and quantum well structures composing antimonide lasers devices. Special emphasis was put on the aluminium precursor and its relation to AlGaSb and AlGaAsSb materials properties. The crystalline quality of the layers grown with two different Al precursors was compared, very good structural quality films were obtained. The results suggested a substantial influence of precursors pre-reactions on the epitaxial process. The oxygen contamination was measured by SIMS, which confirmed its dependence on the precursor choice. We also optimised the GaSb substrate thermal treatment to deposit high quality GaSb homoepitaxial layers. Quaternary InGaAsSb layers were obtained even within the predicted miscibility gap, when arsenic content reached high above 10% values. InGa(As)Sb/AlGa(As)Sb quantum wells were grown and their optical properties were characterised by photoluminescence and photoreflectance spectroscopy. Type-I quantum wells showed a fundamental optical transition in the 1.9-2.1 µm range at room temperature. The epitaxial technology of the structures was subjected to an optimisation procedure. The investigated layers and heterostructures can be considered for application in laser devices.
7
Fourierowska spektroskopia fotoluminescencyjna i fotoodbiciowa struktur półprzewodnikowych przeznaczonych na zakres średniej i długofalowej podczerwieni
Motyka M., Sęk G., Misiewicz J.
Elektronika : konstrukcje, technologie, zastosowania
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2011
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Vol. 52, nr 10
37-39
PL
W pracy przedstawiono wyniki badań spektroskopowych struktur półprzewodnikowych prowadzonych w Zespole Optycznej Spektroskopii Nanostruktur Instytutu Fizyki Politechniki Wrocławskiej w zakresie widmowym średniej i długofalowej podczerwieni. Zaprezentowano możliwości jakie daje stosowanie spektroskopii modulacyjnej, wspartej spektroskopią fotoluminescencyjną, do wyznaczania parametrów fizycznych istotnych z punktu widzenia konstruowaniu urządzeń takich jak np. źródła promieniowania laserowego. W pierwszej części przedstawiono układ pomiarowy do spektroskopii modulacyjnej bazujący na spektrometrze Fouriera jak również wyniki badań zarówno studni kwantowych I rodzaju InGaAsSb/GaSb jak i II rodzaju GaSb/AlSb/ InAs/GaInSb/InAs/AlSb/GaSb do zastosowań emiterowych i detektorowych w zakresie 2-6 μm . W drugiej części przedstawione zostały rezultaty badań warstw HgCdTe o różnej koncentracji atomów kadmu przeznaczonych do zastosowań w czujnikach gazów w zakresie fal 5... 15 μm jak również rezultaty pomiarów fotoluminescencyjnych w obszarze przejść wewnątrzpodpasmowych dla supersieci GaAs/AIGaAs, będących podstawą laserów kaskadowych na zakres emisji 10...15 μm. Ponadto, zaproponowano eksperyment różnicowej spektroskopii odbiciowej pozwalający na szybką charakteryzacja optyczną (w czasie rzędu pojedynczych minut a nawet sekund) struktur półprzewodnikowych w szerokim zakresie spektralnym 1... 15 μm.
EN
In this work, we show the results of optical studies on low-dimensional structures realized in the Laboratory for Optical Spectroscopy of Nanostructures at Institute of Physics Wrocław University of Technology in the spectral range of mid and long wavelength infrared. In the first part there have been shown the advantages and opportunities which gives the modulation spectroscopy gives for the case of structures as InGaAsSb/GaSb type I and GaSb/AlSb/InAs/GaInSb/InAs/AlSb/GaSb type II quantum wells. In the second part, there are presented the results of optical characterization on HgCdTe layers with different Cd atoms content and also on GaAs/AlGaAs superlatticess in the range of intersubband transitions. Additionally, it has been also introduced a fast differential technique which allowed to measure the modulation-like spectra in the very short time scale (single minutes or even seconds) in the broad spectral range (1 ...15 μm).
8
Content available Pomiary właściwości elektrycznych nanokompozytów (CoFeZr)x + (Al2O3)1-x
Kołtunowicz T.
Pomiary Automatyka Kontrola
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2007
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R. 53, nr 11
44-46
PL
W pracy przedstawiono wyniki pomiarów właściwości elektrycznych nanokompozytów (CoFeZr)x + (Al2O3)1-x w oparciu o prąd przemienny o częstotliwości z zakresu od 50 Hz do 1 MHz. Pomiary wykonano w zakresie temperatur od 77 K do 373 K. Przeprowadzono analizę uzyskanych wyników i zaproponowano sposób przenoszenia ładunków elektrycznych pomiędzy studniami kwantowymi.
EN
The paper presents the results of the measurements of the electrical properties of (CoFeZr)x + (Al2O3)1-x nanocomposites performed on the alternating current in the frequency range from 50 Hz to 1 MHz. The measurements were done in the temperature range from 77 K to 373 K. The analysis of the results were performed and the mechanism of the carrying electric charges between quantum wells was proposed.
9
Content available remote Characteristics of quantum beats in InGaN/GaN quantum well
Gao F., Xiong G.
Optica Applicata
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2005
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Vol. 35, nr 4
919-926
EN
A L-type three level atom in the InGaN/GaN quantum wells is formed by the lowest energy level of conductive electrons and the highest sub-bands of light and heavy hole. With the excitation of the coherent light field, a quantum beat spectrum is obtained. The quantum beat spectrum can be calculated by using the theory of effective mass. Quantum beats do not exist in all polarization directions. The influence of quantum well width and the concentration of In on the spectra of quantum beats is also discussed.
10
Content available remote Angle-resolved photoemission of ultrathin Pb films on Si(111)-(6x6) Au: quantum size effect
Kisiel M.
Optica Applicata
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2005
|
Vol. 35, nr 3
443-448
EN
The electronic band structure of extremely thin (from 1 to 8 monoatomic layer (ML) thick) epitaxial Pb(111) films grown at low temperatures in ultrahigh vacuum (UHV) condition on Si(111)-(6x6)Au substrate is studied with angle-resolved photoelectron spectroscopy (ARPES). The morphology of the Pb film is determined with scanning tunneling microscopy (STM). Normal-emission photoelectron spectra recorded at the sample temperature of 130 K reveal quantum well states (QWS) characteristic of quantization perpendicular to the film surface. The energies of these states as a function of the number of the Pb(111) monoatomic layers are determined and compared with calculated in terms of the Bohr-Sommerfeld phase accumulation model.
11
Content available remote Control of ferromagnetism in Cd1-xMnxTe quantum wells
Tatarenko S., Bertolini M., Maslana W., Boukari H., Gilles B., Cibert J., Ferrand D., Kossacki P., Gaj J. A.
Opto-Electronics Review
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2003
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Vol. 11, No. 2
133-138
EN
New structures aiming at controlling ferromagnetic properties of diluted magnetic semiconductors quantum wells are presented. The carrier density is monitored by applying voltage in p-i-n diode or adjusting a distance between quantum well and surface. Surface doping was successfully applied to obtain samples with CdMnTe quantum well with up to 9.3% Mn concentration.
12
Content available remote Intersubband transitions in n-type quantum well systems
Załużny M.
Opto-Electronics Review
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1999
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Vol. 7, No. 2
81-86
EN
Specific properties of intersubband transitions in n-type semiconductor quantum well structures are reviewed. Some interesting aspects of coupling of infrared radiation with intersubband transition in multiple quantum well structures are also considered. Recent achievements in intersubband emission are then discussed with specific emphasise on the quantum cascade lasers.
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