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EN
A theoretical study of electronic structures and optical properties of GaInNAs/GaAs quantum wells has been performed. The inhomogeneous distributions of indium and nitrogen atoms along the growth direction were discussed as the main factors having significant impact on the QWs absorption efficiency. The study was performed by applying the band anticrossing model combined with the envelope function formalism and based on the material parameters which can be found in the literature. Indeed, the electronic band structure of 15 nm thick uniform Ga0.7In0.3N0.02As0.98/GaAs QW was computed together with electronic structures of several types of inhomogeneous QWs, with the same total content of In and N atoms. It was found that presented inhomogeneities lead to significant quantum wells potential modifications and thus to spatial separation of the electrons and holes wave functions. On the other hand, these changes have a significant impact on the absorption coefficient behavior. This influence has been studied on the basis of simulated photoreflectance spectra, which probe the absorption transitions between QW energy subbands. The electronic structure of inhomogeneous QWs under the influence of electric field has also been studied. Two different senses of electric field vector (of p-i-n and n-i-p junctions) have been considered and thus, the improvement of such types of QWs-photodetectors based on inhomogeneous GaInNAs QWs has been proposed.
EN
The work presents doping characteristics and properties of high Si-doped InGaAs epilayers lattice-matched to InP grown by low pressure metal-organic vapour phase epitaxy. Silane and disilane were used as dopant sources. The main task of investigations was to obtain heavily doped InGaAs epilayers suitable for usage as plasmon-confinement layers in the construction of mid-infrared InAlAs/InGaAs/InP quantum-cascade lasers (QCLs). It requires the doping concentration of 1×10¹⁹ cm⁻³ and 1×10²⁰ cm⁻³ for lasers working at 9 μm and 5 μm, respectively. The electron concentration increases linearly with the ratio of gas-phase molar fraction of the dopant to III group sources (IV/III). The highest electron concentrations suitable for InGaAs plasmon-contact layers of QCL was achieved only for disilane. We also observed a slight influence of the ratio of gas-phase molar fraction of V to III group sources (V/III) on the doping efficiency. Structural measurements using high-resolution X-ray diffraction revealed a distinct influence of the doping concentration on InGaAs composition what caused a lattice mismatch in the range of –240 ÷ –780 ppm for the samples doped by silane and disilane. It has to be taken into account during the growth of InGaAs contact layers to avoid internal stresses in QCL epitaxial structures.
EN
Quantum cascade laser is one of the most sophisticated semiconductor devices. The active region of the quantum cascade laser consists of hundreds thin layers, thus the deposition precision is the most crucial. The main technique for the fabrication of quantum cascade laser structure is molecular beam epitaxy, however, the prevalence of metalorganic vapour phase epitaxy techniques in the fabrication of semiconductor structures causes a perpetual work on the improvement production of the entire quantum cascade laser structure by the metalorganic vapour phase epitaxy. The paper presents technological aspects connected with the metalorganic vapour phase epitaxy growth of InGaAs/AlInAs low-dimensional structures for quantum cascade laser active region emitting ~9.6 μm radiation. Epitaxial growth of superlattice made of InGaAs/AlInAs lattice matched to InP was conducted at the AIXTRON 3x2″ FT system. Optical and structural properties of such heterostructures were characterised by means of high resolution X-ray diffraction, photoluminescence, contactless electroreflectance and scanning electron microscope techniques. Epitaxial growth and possible solutions of structure improvements are discussed.
EN
In this work, the authors present the results of optical characterization of GaAs-based multiple quantum well heterostructures, together with energy band structure analysis. The optical properties were investigated by applying photoluminescence spectroscopy. Structures with GaInNAs, GaInAs and GaNAs multiple quantum wells emitting around 1 μm, grown by atmospheric pressure metalorganic vapor phase epitaxy, were compared in this work. The role of nitrogen in quantum well carriers confinement potential was analysed. The photoluminescence intensities of the samples were correlated with the analysis of energy band structures and the overlaps of the carriers’ wave functions. In addition, the main carrier activation energies were estimated based on photoluminescence temperature dependence and the Arrhenius plots analysis. It was deduced that the thermal photoluminescence decay is most probably related to the escape of electrons whereas the holes, independently of the potential well depth, are additionally confined by the local inhomogeneities or by the Coulomb interaction with the confined electrons.
EN
Conventional deep level transient spectroscopy (DLTS) and high-resolution Laplace DLTS techniques were used to study electrical properties of deep-level defects in dilute GaNAs epitaxial layers grown by atmospheric-pressure metalorganic vapourphase epitaxy (APMOVPE) on the GaAs substrate. Three samples with nitrogen concentrations of 1.2 %, 1.6 % and 2.7 % were investigated. In DLTS and LDLTS spectra of the samples, four predominant electron traps were observed. On the basis of the obtained electrical parameters and previously published results, one of the traps was associated with N-related complex defects, while the other traps with common GaAs-like native defects and impurities, called EL6, EL3 and EL2.
PL
Kwantowe lasery kaskadowe są jednymi z najbardziej wyrafinowanych przyrządów półprzewodnikowych. Znajdują zastosowanie m. in. w spektroskopii fotoakustycznej, diagnostyce medycznej czy detekcji śladowych ilości niebezpiecznych gazów. Niektóre z tych aplikacji wymagają pracy ciągłej lasera, w temperaturze pokojowej. Aby zapewnić odpowiednie warunki pracy, niezbędne jest zastosowanie wydajnej techniki odprowadzania ciepła z obszaru rdzenia lasera. Jedną z możliwości jest osadzenie wysokorezystywnych warstw InP:Fe. W niniejszej pracy zaprezentowano etapy opracowywania technologii InP:Fe do zastosowań w kwantowych laserach kaskadowych. Warstwy były osadzone techniką LP-MOVPE na stanowisku firmy Aixtron. Jako źródeł materiałów grup III oraz V użyto odpowiednio: TMIn oraz PH3 (100%), natomiast atomy żelaza pozyskano z CP2 Fe. Przeprowadzono diagnostykę otrzymanych struktur za pomocą takich technik jak HRXRD, AFM czy pomiary elektryczne I-V.
EN
Quantum cascade lasers are one of the most sophisticated semiconductor devices. Their main applications are photoacoustic spectroscopy, medical diagnostics and harmful gas sensing. Some of them need continuous wavelength operation mode at room temperature. In order to assure proper working conditions it is necessary to apply efficient technics of heat dissipation from the laser core. One of the possibilities is to use highly-resistivity InP:Fe layers. In the present work there is elaboration of InP:Fe technology presented. Layers were deposited using LP-MOVPE technique at the AIXTRON system. There were TMIn, PH3 and Cp2Fe materials used as a group III, V and dopant sources. Test structures were investigated by the means of HRXRD, AFM and I-V measurement techniques.
PL
Znajomość podstawowych parametrów modelu jednodiodowego ogniwa słonecznego pozwala na porównanie parametrów ogniw wytwarzanych różnymi technologiami. Ponadto, umożliwia symulowanie pracy ogniw słonecznych oraz analizowanie ich modeli zastępczych. W pracy omówiono właściwości funkcji specjalnej Lamberta W oraz przedstawiono jej wykorzystanie do wyznaczania parametrów jednodiodowego modelu zastępczego ogniwa na podstawie zmierzonych charakterystyk I–V: ciemnych i jasnych.
EN
The knowledge of single diode model parameters is essential for comparison of solar cells fabricated with different methods. Moreover, it enables the simulation of solar cell devices and analysing their equivalent circuits. In this work we present the single diode model of solar cell, the properties of Lambert W function and its application for determining the single diode model parameters, based on measured dark and illuminated I–V characteristics.
EN
Tandem (two p-n junctions connected by tunnel junction) and multijunction solar cells (MJSCs) based on AIIIBV semiconductor compounds and alloys are the most effective photovoltaic devices. Record efficiency of the MJSCs exceeds 44% under concentrated sunlight. Individual subcells connected in series by tunnel junctions are crucial components of these devices. In this paper we present atmospheric pressure metal organic vapour phase epitaxy (AP-MOVPE) of InGaAsN based subcell for InGaAsN/GaAs tandem solar cell. The parameters of epitaxial structure (optical and electrical), fabrication process of the test solar cell devices and current-voltage (J-V) characteristics are presented and discussed.
PL
Kwantowe lasery kaskadowe (QCLs), tzw. lasery unipolarne, które emitują fale o długości z zakresu okna atmosferycznego 3…5 μm, wymagają zastosowania układu materiałowego o dużej nieciągłości pasma przewodnictwa i bardzo dobrej przewodności cieplnej. Wymagania te spełnia układ materiałowy InGaAs/AlInAs/InP. W pracy przedstawiono wyniki badań związanych z epitaksją związków potrójnych InGaAs, dopasowanych sieciowo do InP, przy zastosowaniu niskociśnieniowej metody MOVPE. Pierwszym etapem badań było opracowanie kinetyki wzrostu niedomieszkowanych warstw In- GaAs, dopasowanych sieciowo do InP. Otrzymane warstwy wykazały bardzo dobre właściwości optyczne, co zostało potwierdzone wynikami pomiarów fotoluminescencji. Morfologia tych warstw, badana przy użyciu mikroskopu AFM, wykazała tarasowy wzrost typu „step-flow” i atomową gładkość powierzchni. Kolejnym etapem prowadzonych badań są prace technologiczne związane z domieszkowaniem heterostruktury InGaAs/InP krzemem.
EN
Quantum cascade lasers (QCL) so-called unipolar lasers, which emit light with wavelength at range of atmospheric window 3÷5 μm, require construction from the material system with sufficient conduction band discontinuity and high thermal conductivity. Such requirements are fulfilled by InGaAs/AlInAs/InP. In these paper are shown results of investigation of metalorganic vapor phase epitaxy of ternary alloy InGaAs lattice matched to InP. Grown layers have good optical properties, what is confirmed by photoluminescence measurements. Surface morphology of described samples tested by AFM exhibits step-flow growth and atomic scale surface smoothness. The next stage of ours research will be focused on n-type doping of InGaAs/InP heterostructure with SiH4 as a dopant source.
PL
Wielozłączowe ogniwa słoneczne na bazie półprzewodników złożonych AIIIBV należą do najbardziej wydajnych przyrządów fotowoltaicznych. Sprawność konwersji takich ogniw przekracza 40% przy zastosowaniu skoncentrowanego promieniowania słonecznego. Ważnymi elementami w konstrukcji takiego przyrządu są poszczególne podogniwa wykonane z różnych materiałów półprzewodnikowych. W niniejszej pracy przedstawiono technologię AP-MOVPE dolnego podogniwa na bazie InGaAsN oraz wyniki charakteryzacji otrzymanej struktury epitaksjalnej. Ponadto zaprezentowano wyniki pomiarów J-V wytworzonych ogniw słonecznych typu p-i-n.
EN
Multijunction solar cells (MJSCs) based on AIIIBV semiconductor compounds are the most effective photovoltaic devices. Efficiency of the MJSC devices exceeds 40% under concentrated sunlight. Individual subcells based on different semiconductors are crucial components of tandem solar cell. In this papers we describe AP-MOVPE technology of the bottom InGaAsN subcell and characterization of its epitaxial structure. Moreover, the fabrication process of the test solar cell structure and J-V measurement results are presented and discussed.
11
Content available remote Electro-optical properties of diluted GaAsN on GaAs grown by APMOVPE
EN
In this paper we report on the optical and electrical studies of single GaAs1-xNx epitaxial layers grown on GaAs substrates by means of atmospheric pressure metal organic vapour phase epitaxy (APMOVPE). Three kinds of samples with 1.2 %, 1.6 % and 2.7 % nitrogen content were studied. Optical properties of the layers were investigated with the use of room temperature transmittance and reflectance measurements. Subsequently Schottky Au–GaAs1-xNx contacts were processed and characterized by current-voltage (I-V) and capacitance-voltage (C-V) measurements within 80 – 480 K temperature range. From the I-V and C-V characteristics the ideality factor, series resistance and built-in potential were determined. Obtained diodes can be used for further studies on defects with the use of DLTS method.
EN
Determination of indium and nitrogen content in InGaAsN quantum wells (QWs) is often based on the analysis of highresolution X-ray diffraction (HRXRD) measurements. The comparison of diffraction curves of two similar samples, with and without nitrogen, together with an assumption of constant indium incorporation efficiency during the growth of layers with and without nitrogen, may lead to a large deviation in the determined In and N content. The HRXRD curve simulations supported by bandgap determination and calculations seem to be a solution of this problem. Comparison of the results achieved from simulated HRXRD curves with the calculations of all QWs transitions measured by contactless electro-reflectance (CER) can lead to reduction of deviations in composition determination of InGaAsN quantum wells. The proposed algorithm was applied for investigation of InGaAsN QWs grown by atmospheric pressure metalorganic vapor phase epitaxy (APMOVPE).
EN
In this paper there was presented the brief overview of the semiconductor structures epitaxial growth including different modes of epitaxial growth and different epitaxial techniques. The modes of the growth which enable to fabricate semiconductor structures, both with almost perfect planar layers and with more advanced three dimensional objects, were discussed. Several techniques of growth of semiconductor materials and heterostructures were presented together with concise information about the advantages and disadvantages of each of them. Technological requirements which should be fulfilled in order to fabricate advanced semiconductor devices and few aspects of the epitaxai growth were talked over as well.
PL
W pracy przedstawiono podstawowe zagadnienia dotyczące epitaksji związków półprzewodnikowych, wliczając w to omówienie różnych modów epitaksjalnego wzrostu oraz różnych technik epitaksji. Omówione zostały mody epitaksjalnego wzrostu umożliwiające wytwarzanie struktur atomowo gładkich warstwa po warstwie oraz bardziej zaawansowanych struktur trójwymiarowych. Przedstawione zostały różne techniki epitaksji związków półprzewodnikowych wraz z krótką charakterystyką ich wad i zalet. Omówione zostały również wymagania technologiczne jakie muszą zostać spełnione w celu wytwarzania zaawansowanych przyrządów pół przewodnikowych.
PL
Wielozłączowe ogniwa słoneczne na bazie półprzewodników złożonych AlIIBV należą do najbardziej wydajnych przyrządów fotowoltaicznych. Istotnym elementem konstrukcyjnym takiego ogniwa jest złącze tunelowe, umożliwiające połączenie elektryczne i optyczne pomiędzy sąsiednimi podogniwami minimalnych stratach. Niniejsza praca omawia funkcje złącza tunelowego oraz wymagania konstrukcyjne stawiane przez ten przyrząd. Dodatkowo przedstawione zostały prace autorów dotyczące epitaksjalnego wzrostu wytworzenia testowej struktury diody tunelowej na bazie GaAs.
EN
Multijunction solar cells (MJSCs) based on AIIIBV semiconductor compounds are the most effective photovoltaic devices. One of the most important parts of their construction is a tunnel junction (TJ), which is designed for series electrical connection between individual subcells. This work describes the main principles of the tunnel junction work and requirements for MJSC applications. Moreover the results concerning an epitaxial growth and fabrication of the test GaAs-based tunnel diodes are presented and discussed.
PL
Stopy półprzewodnikowe AIIIBV z małą zawartością azotu, zwane „rozrzedzonymi azotkami”, są intensywnie badane ze względu na swoje unikalne właściwości i potencjalne zastosowanie w laserach IR i wydajnych wielozłączowych ogniwach słonecznych. Epitaksja (MOVPE lub MBE) tych materiałów jest trudna, proces kontrolowany jest głównie przez temperaturę wzrostu i koncentrację azotu w fazie gazowej. Precyzyjne wyznaczenie składu stopu InGaAsN jest złożone i wymaga zastosowania wielu technik pomiarowych. W pracy opisano technologię i optyczne właściwości niedomieszkowanych studni kwantowych 3×InGaAsN/GaAs otrzymanych metodą epitaksji z fazy gazowej z zastosowaniem związków metaloorganicznych przy ciśnieniu atmosferycznym (AP MOVPE). Testowe struktury epitaksjalne, otrzymane w różnych warunkach, zastosowano jako obszar aktywny fotodetektorów MSM. Omówiono i przeanalizowano wpływ parametrów osadzania na optyczne właściwości struktur MQW oraz ciemne i oświetlone charakterystyki dc I-V fotodetektorów MSM.
EN
AIIIBV semiconductor alloys with small amount of nitrogen, so called dilute nitrides have been extensively studied due to their unusual properties which make them very attractive for IR lasers and very efficient multijunction solar cells. The epitaxial process (MOVPE or MBE) of these materials is very difficult and strongly depends on the growth temperature and the nitrogen concentration inside an epitaxial reactor Additionally, a precise determination of the quaternary InGaAsN alloys composition is complicated and requires applying a lot of examination methods. This work presents the technology and optical properties of undoped triple quantum wells 3×InGaAsN/GaAs grown by atmospheric pressure metal organic vapour phase epitaxy (AP MOVPE). Epitaxial test structures obtained at different process conditions are used as the active regions of metal-semiconductor-metal (MSM) photodetectors. The influence of the growth parameters on the optical properties of MQW structures and measured dark and illuminated dc I-V characteristics of MSM detectors is analysed and discussed.
PL
Wzrost światowego zapotrzebowania na energię elektryczną wymusza rozwój badań w zakresie alternatywnych źródeł energii. Fotowoltaika wydaje się być perspektywicznym i nieszkodliwym dla środowiska sposobem konwersji promieniowania słonecznego na sygnał elektryczny. Obok powszechnych już ogniw i modułów krzemowych aktualnie badane są wysokosprawne, wielozłączowe ogniwa bazujące ma materiałach AIIIBV. W niniejszej pracy przedstawiono wyniki dotyczące zastosowania poczwórnych związków półprzewodnikowych InGaAsN w konstrukcji ogniwa słonecznego p-i-n.
EN
The worldwide increase of electric power consumption forces the development of alternative sources of energy. Photovoltaics seems to be a promising and harmless to the natural environment method of producing electrical power. Besides silicon cells and panels, present researches are focused on high efficiency and multijunction solar cells based on AIIIBV semiconductors. This paper presents the results of application of the new InGaAsN semiconductor compounds in the p-i-n solar cell construction.
PL
W artykule przedstawione zostały parametry fotodetektorów MSM wykonanych na warstwach czynnych GaAsN/GaAs i MQW InGaAsN/GaAs. Wszystkie warstwy czynne optycznie wykonane zostały w technologii epitaksji MOVPE. W warstwach GaAsN/GaAs struktura czynna GaAsN miała grubość 100...330 nm, a zawartość atomów azotu mieściła się w zakresie 0,85...2,2%. Struktury MQW InGaAsN/GaAs stanowiły trzy studnie InGa-AsN o grubości 15 nm i zawartości 11% indu rozdzielone barierami GaAs o grubości 30 nm. W pracy przedstawiono charakterystyki prądowo-napięciowe detektorów MSM bez i z oświetleniem, co pozwala określić podstawowe parametry wykonanych fotodetektorów. Z uzyskanych wyników widać bardzo wyraźny wpływ składu materiałowego wykonanych heterostruktur na fotoprąd i czułość wykonanych fotodetektorów MSM.
EN
In this paper the comparison of GaAsN/GaAs and InGaAsN/GaAs MSM photodetectors has been presented. All of the devices were made by MOVPE technology. The GaAsN/GaAs MSM devices were made on undoped GaAsN layers with concentration of nitrogen varied from 0.85...2.2%. The thickness of these layers was from 100...330 nm. The InGaAsN/GaAs active layer for MSM detectors consisted of triple InGaAsN MQW with 11% of indium in 15 nm thick QWs layers and 30 nm thick GaAs barrier layers. The dark and illuminated l-V characteristics of the designed devices were presented. The photoresponse characteristics have shown a strong influence of material composition on the MSM photocurrent for both GaAsN/GaAs and InGaAsN/GaAs heterostructures.
EN
This paper presents the influence of the AP-MOVPE epitaxial process growth temperature on the optical and structural properties of heterostructures containing InGaAsN quantum wells. The best optical and structural features were observed for MQW structure grown in highest temperature. This structure (sample NI 46) was applied in the test p-i-n solar cell construction. Measured dc I-V characteristics exhibit electrical response under the optical excitation by a discrete laser diode with λ = 980 nm, what confirms the usability of InGaAsN semiconductor compounds in solar cell applications.
EN
The nitrogen-containing AIIIBV semiconductor alloys, so-called diluted nitrides (AIIIBV-N, have been extensively studied recently. Unusual properties of these materials make them very promising for applications in lasers and very efficient multijunction solar cells. This work presents the technology and properties of undoped GaAs1-xNxGaAs heterostructures used as active regions in the construction of metal-semiconductor-metal (MSM) photodetectors. The atmospheric pressure metal organic vapour phase epitaxy (APMOVPE) was applied for growing MSM test structures. Their structural and optical properties were examined using high resolution X-ray diffraction (HRXRD), photoluminescence (PL), and photoreflectance spectroscopy (PR). Chemical wet etching was applied for forming an active region and a multifinger Schottky metallization was used as MSM contacts. Dark and illuminated current-voltage characteristics were measured. Based on the obtained results, the main detector parameters as responsivity and spectral response were estimated.
20
Content available remote Technology and properties of GaAs doping superlattices
EN
Heterojunction and doping superlattices are widely used in many advanced semiconductor devices such as resonant tunnelling diodes, optical modulators, cascade lasers, tunable light emitting diodes and photodetectors. These structures exhibit nonlinear electrooptical properties. Nonlinear processes are governed by the Franz-Keldysh effect and the band-filling effect in the n-i-p-i superlattices and by the quantum-confined Stark effect in the case of n-i-p-i multiple quantum well structures. The paper presents investigations of GaAs n-i-p-i and p-i-p-i doping superlattices grown by atmospheric pressure metal organic vapour phase epitaxy. The properties of the obtained structures were examined using: EC-V method, SIMS spectrometry, photoluminescence and photoreflectance spectroscopy.
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