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1

Badanie kinetyki wzrostu epitaksjalnych warstw lateralnych dla zastosowań fotowoltaicznych

Gułkowski S., Cieślak K., Olchowik J. M., Paprota M., Syroka M., Głowienka R.

Zeszyty Naukowe Politechniki Rzeszowskiej. Budownictwo i Inżynieria Środowiska

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2012

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z. 59, nr 2/II/I

297-302

PL

W artykule przedstawiono rezultaty badań dotyczących kinetyki wzrostu warstw epitaksjalnych otrzymywanych techniką ELO (Epitaxial Lateral Overgrowth – lateralny wzrost warstw epitaksjalnej). Omówiona została metoda przeprowadzenia eksperymentu. Zbadano wpływ parametrów technologicznych procesu tj. szybkości chłodzenia, rozmiarów okien Si, na kinetykę wzrostu lateralnego na podłożu krzemowym.

EN

Epitaxial Lateral Overgrowth (ELO) may be promising technique in photovoltaics application due to possibility of producing high quality Si epitaxial layers on silicon substrates. The advantage of this method is that density of the dislocations in new layer is less than in the substrate. The main goal of this method is to obtain as wide and as thin structures as possible. For this reason our research was concentrated on technological parameters of the growth process and its influences on width of the layer.

2

Influence of dielectric coverage on photovoltaic conversion of silicon solar cells obtained by epitaxial lateral overgrowth

Cieslak K., Gulkowski S., Olchowik J. M.

Materials Science Poland

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2012

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Vol. 30, No. 3

274--277

EN

This work presents an analysis of the influence of SiO2 dielectric coverage of a Si substrate on the solar-cell efficiency of Si thin layers obtained by epitaxial lateral overgrowth (ELO). The layers were obtained by liquid phase epitaxy (LPE). All experiments were carried out under the following conditions: initial temperature of growth: 1193 K; temperature difference ^T = 60 K; ambient gas: Ar; metallic solvent: Sn+Al; cooling rates: 0.5 K/min and 1 K/min. To compare the influence of the interior reflectivity of photons, we used two types of dielectric masks in a shape of a grid etched in SiO2 along the <110> and <112> directions on a p+ boron-doped (111) silicon substrate, where silicon dioxide covered 70 % and 80 % of the silicon surface, respectively. The results obtained in this work depict the correlation between the interior efficiency and percentage of SiO2 coverage of the substrate of the ELO solar cells.

3

Finite element method simulation of interface evolution during epitaxial growth

Gulkowski S., Olchowik J. M., Cieslak K., Moskvin P. P.

Materials Science Poland

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2012

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Vol. 30, No. 4

414--418

EN

Epitaxial Lateral Overgrowth (ELO) is a method of epitaxial growth on a partially masked substrate. It can be a promising method for photovoltaic applications due to a possibility of producing thin and high quality silicon substrates. Since the mask prevents propagation of the substrate dislocations to the laterally overgrown parts of the ELO layer they are characterized by a lower dislocation density than the substrate. It means that it is possible to fabricate good quality solar cells on a poor quality Si substrate. The main goal of the research is to obtain a higher growth rate in the lateral direction than in the direction normal to the substrate. The epilayer growth kinetics depends on many technological factors, basically the growth temperature, the cooling rate, the solvent and the mask filling factor. For this reason the best way to achieve the goal is a computational analysis of the epitaxial layer growth process. This work presents a two-dimensional computational study of such a process of growth for different technological conditions. The computational model is based on the assumption of pure diffusion control growth.

4

Polyassociative Model of A2B6 Semiconductor Melt and p-T-x Phase Equilibria in Zn-Cd-Te System

Moskvin P., Antonov M., Olchowik G., Olchowik J., Zdyb A., Gulkowski S., Sadowski W.

TASK Quarterly : scientific bulletin of Academic Computer Centre in Gdansk

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2011

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Vol. 15, No 1

121-130

EN

This work presents a numerical analysis of p-T-x phase equilibrium in the Zn-Cd-Te ternary system in the framework of the polyassociative solution model. On the basis of the experimental data on p-T-x phase equilibrium in the ternary system, thermodynamic functions describing the formation of liquid associates were found. It was shown that the results of the mixing of components in the Zn-Cd-Te ternary melt are related to the occurrence of ZnCdTe and ZnCdTe3 associates. Dissociation parameters of these complexes were calculated and subsequently used in order to efficiently describe p-T-x phase equilibrium of the system in a wide temperature range.

5

New Approach to the Determination of Phase Equilibrium in the Zn-Te System

Moskvin P., Olchowik J., Olchowik G., Zdyb A., Gulkowski S., Sadowski W.

TASK Quarterly : scientific bulletin of Academic Computer Centre in Gdansk

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2011

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Vol. 15, No 2

209-217

EN

The polyassociative model of the liquid phase was applied to describe the phase equilibrium in the Zn-Te system. The thermodynamic functions describing the formation of liquid associates were obtained, taking into account the experimental data on the p-T-x equilibrium in the system. The model of polyassociative solutions with the parameters obtained in this work satisfactorily describes the p-T-x diagram of the system. The numerical results of the analysis of the phase equilibrium confirmed the possibility of applying the polyassociative model to the Zn-Te system in a wide temperature range.

6

Wpływ wewnętrznego lustra na wydajność kwantową fotoogniw wytwarzanych w oparciu o krzemowe warstwy lateralne

Cieślak K., Olchowik J. M., Gułkowski S.

Elektronika : konstrukcje, technologie, zastosowania

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2011

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Vol. 52, nr 4

20-21

PL

W pracy przedstawiono rezultaty badań krzemowych ogniw słonecznych, wytwarzanych za pomocą, epitaksji z fazy ciekłej LPE (Liquid Phase Epitaxy). Epitaksja z fazy ciekłej pozwala w ekonomiczny sposób uzyskiwać cienkie monokrystaliczne warstwy, które mają również zastosowania w fotowoltaice. W prowadzonych badaniach zastosowano pewną modyfikację klasycznej metody LPE - wzrost na częściowo maskowanym dielektrykiem podłożu krzemowym. Taki sposób nosi nazwę epitaksji lateralnej ELO (Epitaxial Lateral Overgrowth) i pozwala na uzyskanie warstw o znacznie mniejszej gęstości defektów w stosunku do gęstości defektów w podłożu wzrostowym [1], co więcej warstwa dielektryka obecna wewnątrz struktury fotoogniwa stanowi lustro dla niezaabsorbowanych fotonow, co pozwala na wydłużenie ich drogi optycznej. W pracy porównano wpływ wewnętrznego lustra z dielektryka SiO₂ na wydajność kwantową, badanych fotoogniw.

EN

This work contains research of silicon thin film solar cells obtained from a lateral overgrowth liquid phase epitaxy (LPE). Liquid phase epitaxy is an economic method that enables to produce thin, monocrysallic films for photovoltaic applications. Presented research are based on some modification of the LPE method - it uses partially masked by dielectric, growing silicon substrates. This modification is called epitaxial lateral overgrowth (ELO) and enables to obtain lower defects density in a growing layer comparing to a growing substrate [1]. Moreover dielectric layer inside a solar cell structure forms an inner mirror for photons which are not absorbed in the active layer. This work presents influence of the inner mirror formed from SiO₂ efficiency of the solar cells.

7

Optymalizacja procesu epitaksji z fazy ciekłej do zastosowań fotowoltaicznych

Cieślak K., Olchowik J. M., Gułkowski S.

Zeszyty Naukowe Politechniki Rzeszowskiej. Budownictwo i Inżynieria Środowiska

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2010

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z.57[271], nr 4

83-88

PL

W pracy zaprezentowano technologię wytwarzania cienkich warstw krzemowych do zastosowań fotowoltaicznych. Proces oparty jest o technologię epitaksji z fazy ciekłej. Analiza rezultatów przedstawiająca gęstość prądu zwarcia w zależności od parametrów epitaksji z fazy ciekłej pozwala na znalezienie optymalnych warunków technologicznych dla procesu.

EN

This work present a technology of producing thin film silicon layers for photovoltaic applications which is based on a liquid phase epitaxy. Analysis of the results obtained in the experiment enables to establish a short circuit current density dependence on the liquid phase epitaxy parameters. This can be used to find optimal conditions for the process.

8

Ion milling-assisted study of defect structure of HgCdTe films grown by liquid phase epitaxy

Izhnin I. I., Denisov I. A., Smirnova N. A., Pociask M., Mynbaev K. D.

Opto-Electronics Review

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2010

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Vol. 18, No. 3

328-331

EN

Ion milling, as a tool for ''stirring'' defects in HgCdTe by injecting high concentration of interstitial mercury atoms, was used for studying films grown by liquid phase epitaxy (LPE) on CdZnTe substrates. The films appeared to have very low residual donor concentration (∼10¹⁴ cm⁻³), yet, similar to the material grown by molecular beam epitaxy, contained Te-related neutral defects, which the milling activated electrically. It is shown that ion milling has a stronger effect on HgCdTe defect structure than thermal treatment, and yet eventually brings the material to an ''equilibrium'' state with defect concentration lower than that after low-temperature annealing.

9

Technologia wytwarzania krzemowych warstw lateralnych dla zastosowań PV

Jóźwik I., Olchowik J. M.

Zeszyty Naukowe Politechniki Rzeszowskiej. Budownictwo i Inżynieria Środowiska

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2006

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z. 40 [229]

247-254

PL

Niniejsza praca prezentuje technikę epitaksji z fazy ciekłej jako ekonomiczną metodę uzyskiwania cienkich warstw krzemowych dla zastosowań PV. W rezultacie przeprowadzonych badań stwierdzono, że możliwe jest optymalne dobranie warunków technologicznych procesu wzrostu tak, aby otrzymywane warstwy charakteryzowały się minimalną gęstością defektów przy maksymalnej wartości wydłużenia warstw.

EN

This work presents liquid phase epitaxy as a technique of growth of silicon thin layers for PV applications. Results of the investigation show that it is possible to set the experimental conditions of the process of growth to obtain layers characterized by minimum defect density and maximum aspect ratio at the same time.

10

Epitaxial films of GaInPAsSb quinary solid solutions

Kuznetsov V. V., Rubtsov E. R., Kognovitskaya E. A.

Materials Science Poland

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2006

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Vol. 24, No. 4

1057--1066

EN

The method of the obtaining quinary solid solutions on the basis of A IIIBV compounds (GalnPAsSb) with specified properties was developed. New GaInPAsSb/GaSb, GalnPAsSb/InAs heterostructures were obtained to create optoelectronic devices for the 2-5 urn spectral range. The broken-gap type II hetero junction was formed at the InAs/Ga0.92In 0.08P0.05As0.08Sb0.87 heterostructure, and a light-emitting diode was fabricated with the emission intensity maximum at 1.9 žm.

11

Analysis of the processes of silicon epitaxial lateral overgrowth in Ar ambient gas

Jóźwik I., Olchowik J. M.

Materials Science Poland

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2006

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Vol. 24, No. 4

967--973

EN

Liquid phase epitaxy (LPE) and, in particular, epitaxial lateral overgrowth (ELO) is an attractive method of thin film deposition, owing to the simplicity of its technology and a reduced growth temperature. In this paper, we present recent results of the ELO of silicon layers carried out by means of LPE using Ar as an ambient gas, without any addition of hydrogen, potentially explosive gas, which makes this deposition technique a very safe process. The aim of the this work focused on the silicon ELO growth on partially masked substrates was to determine optimal conditions of growth resulting in ELO layers of the maximum aspect ratio and minimum defect density. Data presented herein clearly show that the epitaxial layers characterized by the maximum value of the aspect ratio can be obtained by application of the 0.25°C/min cooling rate. Noteworthy is the fact that in the same conditions the defect density achieves the minimum value of 1.07×104 cm-2, which is the amount smaller by the factor of 10 than the defect density of Si substrates used (1.7×105 cm-2). It confirms the ELO technique as a promising tool for the fabrication of low-defect density silicon layers of good morphology.

12

Study of Sn-Cu-Al-Si phase diagrams for growth of silicon thin film by liquid phase epitaxy

Abdo F., Fave A., Lemiti M., Laugier A., Bernard C., Pish A.

Archives of Metallurgy and Materials

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2006

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Vol. 51, iss. 4

533-537

EN

Silicon thin films are attracting considerable interest as a possible means of achieving low cost solar cells. In order to absorb 90% of the solar spectra, the thickness of such film has to be 30 µm. In this paper we compared LPE growth using pure Sn melt or Sn-Cu alloys at temperature below 800°C and their potential for photovoltaic applications. From Sn melt, one can achieved maximum thickness of 15 µm. Thickness is limited by the low solubility of Si in the melt. However from Sn-Cu solutions, when composition is carefully chosen, solubility is more important. Then thickness as much as 30 m has been obtained. Furthermore, we described experimental technique allowing in situ removal of silicon native oxide prior to the growth.

PL

Krzemowe cienkie warstwy wzbudzają znaczne zainteresowanie jako możliwość uzyskania tanich ogniw słonecznych. Aby zaabsorbowac 90% widma słonecznego, grubość takiej warstwy musi mieć 30 µm. W pracy porównujemy wzrost LPR stosując czystą ciecz Sn lub stopy Sn-Cu w temperaturze poniżej 800°C i ich potencjalne zastosowanie w fotowoltaice. Stosując ciecz Sn można uzyskać maksymalną grubość 15 µm. Grubość jest ograniczona przez niską rozpuszczalność Si w cieczy. Jednak dla roztworów Sn-Cu, gdy skład jest dokładnie określony, rozpuszczalność jest bardziej istotna. W tym przypadku uzyskano grubość dochodzącą do 30 m. Ponadto opisujemy doświadczalne techniki umożliwiające usuwanie “in situ” rodzimego tlenku krzemu poprzedzające wzrost.

13

Struktury epitaksjalne do mikrolaserów z pasywną modulacją dobroci rezonatora

Sarnecki J., Kopczyński K., Mierczyk Z., Skwarcz J., Młyńczak J.

Elektronika : konstrukcje, technologie, zastosowania

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2005

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Vol. 46, nr 2-3

71-72

PL

Pasywne modulatory dobroci mikrolaserów Cr⁴⁺:YAG, Cr⁴⁺:GGG i Co²⁺:YAG otrzymano metodą epitaksji z fazy ciekłej. Cienkowarstwowe struktury o nieliniowej absorpcji tworzyły modulatory mikrolaserów. Otrzymane warstwy charakteryzowano z wykorzystaniem pomiarów XRD, badań spektroskopowych i generacyjnych.

EN

Liquid phase epitaxy technique was used to grow Cr⁴⁺:YAG, Cr⁴⁺: GGG and Co²⁺:YAG thin films as a saturable absorber for passively Q-switched microchip lasers. X-ray diffraction analysis, optical transmission spectra measurements and passive Q-switching experiments were performed to characterize the obtained layers.

14

Strain in epitaxial laterally overgrown structures

Zytkiewicz Z. R.

Opto-Electronics Review

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2001

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Vol. 9, No. 2

142-149

EN

X-ray diffraction and synchrotron x-ray topography methods were used to analyse strain in GaAs layers grown on GaAs and Si substrates by epitaxial lateral overgrowth (ELO) from a liquid phase. We show the laterally overgrown parts of ELO stripes adhere to the SiO₂ mask which results in their downwards bending. The procedure was found which allows to control adhesion of the layers to the mask by adjusting the vertical growth rate of the layers. For the case of GaAs ELO layers grown on Si substrates the ELO stripes bend outwards from the mask due to the tensile strain in the GaAs buffer layer. Recent data published on strain in other than GaAs ELO structures are reviewed and compared with our results.