W poniższej pracy, dwie struktury p-Si/n-ZnMgO zostały scharakteryzowane pod kątem zastosowania w detektorach światła ultrafioletowego (UV). Przeprowadzone zostały pomiary charakterystyk prądowo-napięciowych (I-V), fotoluminescencji (PL) oraz fotoodpowiedzi. Charakterystyki I-V zostały zmierzone w 310 K i pozwoliły stwierdzić, że obie struktury posiadają właściwości prostujące. Pomiary fotoluminescencji i fotoodpowiedzi zostały przeprowadzone w temperaturze pokojowej. Została przeprowadzona dokładna analiza widm fotoluminescencji, które w jednej z próbek ujawniły pasma emisyjne świadczące o obecności defektów. Pomiary fotoodpowiedzi również zostały szczegółowo przeanalizowane, podane zostały główne wady badanych struktur oraz rozwiązania, które mogą przyczynić się do udoskonalenia struktur.
EN
In our paper, two p-Si/n-ZnMgO structures were characterized in terms of applicability in ultraviolet light detectors. A few measurement techniques have been applied: current-voltage (I-V) characteristics, photoluminescence (PL) and photoresponsivity measurements. I-V characteristics were measured at 310 K and allowed us to conlcude, that both of investigated structures have rectifying properties. Photoluminescence and photoresposivity measurements were performed at room temperature. The analysis of PL spectra exhibited emission bands corresponding to defects in one of studied samples. Photoresponsivity spectra were also thoroughly examined – the most important disadvantages of analysed structures were given together with possible solutions, which can be applied in order to obtain well-working UV detectors.
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W pracy zbadano struktury fotowoltaiczne na bazie nanosłupków tlenku cynku pokrytych warstwą ZnMgO, a następnie warstwą ZnO:Al (AZO). Nanosłupki zostały wytworzone na podłożu krzemowym i pokryte nanocząstkami złota lub srebra. Z pomiarów transmisji i odbicia wywnioskowano, że próbki z nanocząstkami srebra odbijają znaczną ilość światła w zakresie widzialnym, co powoduje spadek wydajności kwantowej w tym zakresie. W podczerwieni próbki z nanocząstkami mają wyższą wydajność kwantową niż próbka referencyjna bez nanocząstek. Stwierdzono, że próbka z nanocząstkami złota ma najwyższą wydajność kwantową w całym zakresie czułości 400-800 nm. Ponadto jej sprawność osiąga również najwyższą wartość – 5,79%.
EN
In this article photovoltaic structures based on ZnO nanorods covered with ZnMgO and ZnO:Al (AZO) layers were studied. The nanorods were grown on sillicon and covered with gold or silver nanoparticles. From the transmission and reflection measurments it was concluded that the samples with silver nanoparticles reflect more light in the visible spectra, which cause the decrease in external quantum efficiency for this wavelength range. In the infrared range the samples with nanoparticles have higher external quantum efficiency than the referance sample without the nanoparticles. It was also concluded, that the sample with gold nanoparticles have the highest external quantum efficiency in the wavelength range from 400-800 nm. Furthermore, the sample has the highest efficiency – 5.79%.
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W niniejszym artykule przedstawione zostały wyniki badań defektów w strukturach fotowoltaicznych na bazie CdTe, otrzymanych techniką epitaksji z wiązek molekularnych (MBE). Do charakteryzacji defektów w badanych złączach wykorzystano różne metody pomiarowe, takie jak: charakterystyki prądowo-napięciowe, niestecjonarna spektroskopia głębokich poziomów (DLTS) i fotoluminescencja (PL), mierzone w szerokim zakresie temperatur. Pokazano, że sprawności badanych diod są stosunkowo niskie, na co mają wpływ defekty występujące w ich strukturze. W oparciu o wyniki pomiarów widm DLTS i PL wyznaczono parametry defektów oraz określono źródło ich pochodzenia.
EN
In this article the results of investigations of defects in photovoltaic structures based on CdTe grown by the molecular beam epitaxy (MBE) technique have been presented. For the characterization of defects in the studied junctions various measurement methods have been used, such as: current-voltage characteristics, deep level transient spectroscopy (DLTS) and photoluminescence (PL), measured in a broad temperature range. It has been shown that the efficiency of the investigated diodes are relatively low, what is caused by the defects present in their structure. Based on the results of the DLTS- and PL spectra the parameters of defects have been determined and their possible origin has been discussed.
Our studies focus on test structures for photovoltaic applications based on zinc oxide nanorods grown using a low-temperature hydrothermal method on a p-type silicon substrate. The nanorods were covered with silver nanoparticles of two diameters – 20–30 nm and 50–60 nm – using a sputtering method. Scanning electron microscopy (SEM) micrographs showed that the deposited nanoparticles had the same diameters. The densities of the nanorods were obtained by means of atomic force microscope (AFM) images. SEM images and Raman spectroscopy confirmed the hexagonal wurtzite structure of the nanorods. Photoluminescence measurements proved the good quality of the samples. Afterwards an atomic layer deposition (ALD) method was used to grow ZnO:Al (AZO) layer on top of the nanorods as a transparent electrode and ohmic Au contacts were deposited onto the silicon substrate. For the solar cells prepared in that manner the current-voltage (I-V) characteristics before and after the illumination were measured and their basic performance parameters were determined. It was found that the spectral characteristics of a quantum efficiency exhibit an increase for short wavelengths and this behavior has been linked with the plasmonic effect.
Warstwy tlenku cynku otrzymane metodą osadzania warstw atomowych ALD zostały użyte jako n-typu partner dla p-typu krzemu. Jako przezroczystą górną elektrodę wybrano warstwę tlenku cyku domieszkowaną glinem (tak zwana warstwa TCO – Transparent Conductive Oxide). Użyto tanich podłóż krzemowych o niezoptymalizowanej dla zastosowań fotowoltaicznych grubości. W niniejszej pracy badano proste struktury fotowoltaiczne ZnO/Si w celu redukcji kosztów produkcji energii elektrycznej pozyskiwanej za pomocą ogniw fotowoltaicznych. Zmierzona sprawność zoptymalizowanych częściowo (warstwy ZnO) ogniw fotowoltaicznych wyniosła 6%.
EN
We report on the properties of photovoltaic (PV) structures based on thin films of n-type zinc oxide grown by atomic layer deposition method on a cheap silicon substrate. Thin films of ZnO are used as n-type partner to p-type Si (110) and, when doped with Al, as a transparent electrode. PV structures with different electrical parameters and thicknesses of ZnO layers were deposited to determine the optimal performance of PV structures. The best response we obtained for the structure with ZnO layer thickness of 800 nm. The soobtained PV structures show 6% efficiency.
Semiconductor low-dimensional structures of CdTe quantum dots (QDs) embedded in ZnTe matrix have been investigated by micro-Raman spectroscopy. A reference ZnTe sample (without dots) was also studied for comparison. Both samples were grown by a molecular beam epitaxy technique on the p-type GaAs substrate. The Raman measurements have been performed at room temperature. The samples were excited by an Ar2+ laser of 514.5 nm wavelength. The Raman spectra have been recorded for different acquisition parameters of the measurement. For the reference and QD sample localized longitudinal (LO) phonons of 210 cm–1 wavenumber associated with the ZnTe layer are observed. In the case of QD sample another broadband corresponding to the LO CdTe phonon related to the QD-layer appears at a wavenumber of 160 cm–1. Such behaviour does not exhibit the Raman spectra of the reference sample. Thus the Raman measurements confirm the presence of CdTe layer of quantum dots in the investigated material. Additionally, Raman spectra for both samples exhibit tellurium-related peaks at wavenumbers around 120 cm–1 and 140 cm–1, significantly increasing with laser time exposure. It is shown that the peaks are associated with the formation of Te aggregates on the ZnTe surface due to the laser damage in the ZnTe layer.
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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.
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In this study we present the results of investigations on Schottky Au–GaN diodes by means of conventional DLTS and Laplace DLTS methods within the temperature range of 77 – 350 K. Si-doped GaN layers were grown by Molecular Beam Epitaxy technique (MBE) on sapphire substrates. DLTS signal spectra revealed the presence of four majority traps: two hightemperature and two low-temperature peaks. Using LDLTS method and Arrhenius plots the activation energy and capture cross sections were obtained. For two high-temperature majority traps they are equal to E1 = 0.65 eV, s1 = 8.2 × 10<-16/sup>cm2 and E2 = 0.58 eV, s2 = 2.6 × 10<-15/sup> cm2 whereas for the two low-temperature majority traps E3 = 0.18 eV, s3 = 9.72 × 10<-18/sup> cm2 and E4 = 0.13 eV, s4 = 9.17 × 10<-18/sup> cm2. It was also found that the traps are related to point defects. Possible origin of the traps was discussed and the results were compared with the data found elsewhere [1–5].
The n-type ZnO layers were grown by ALD method on p-type CdTe substrate. I-V characteristics verified rectifying properties of the test ZnO/CdTe solar cell diode and exhibited photovoltaic effect when the junction was exposed to light. The series resistance of the diode, determined from the I-V curves, equals to 36 Ω. Such a high value is responsible for low value of fill factor and efficiency of the solar cell. Photoresponse properties of the studied junction were measured at room temperature. Efficient photoresponse was observed within wavelength range of 400-1000 nm. These results indicate that n-ZnO/p-CdTe junction is suitable for the fabrication of efficient solar cells. It was shown that the thickness of the ZnO layers can be also determined with the help of interference fringes of photoresponse analysis. Further work will involve a better understanding of the properties of window layer and junction formation processes.
In summary, we present in this study the results of studies on the layers of GaAs1-xNx grown on n-type GaAs substrates by atmospheric pressure metal organic vapour phase epitaxy (APMOVPE), Using transmittance, reflectance, photocurrent measurements and empirical expression for Eg a new nitrogen content for the studies samples was obtained. Using dark and illuminated I-V characteristics the main parameters of the Schottky contacts (short-circuit current Isc, open circuit-voltage, Voc, and fill factor, FF) were determined. Obtained contacts are promising for solar cell application.
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