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Injection dependent measurements The minority carrier lifetime is strongly dependent on the injection (excess carrier concentration). From the shape and height of the lifetime curve information about the dominant recombination center as well as trapping center can be deduced. With MDPmap it is possible to measure not only injection dependent lifetime curves but also photoconductivity curves over a very wide range of injection. In the MDPmap and MDPingot up to 4 different lasers can be integrated and hence it is possible to measure not only injection dependent lifetime curves but also photoconductivity curves over a very wide range of injection. Figure 1 displays a comparison of the typical injection range of different known lifetime measuring methods. Because of its extraordinary sensitivity the MDPmap and MDPingot are able to measure over seven decades of injection. Due to bias light and reflection measurements a very good accuracy could be improved profoundly. With MDPmap the whole important injection range can be covered with just one method as demonstrated in figure 2 for 2 different spots on a SiNx passivated mc-Si wafer. Until now it was necessary to use several different methods, which often cannot be compared to each other. With MDP an easy excess to the important injection dependent lifetime curves is possible. For further information please read: [1] S. Rein, Lifetime Spectroscopy - A Method of Defect Characterization in Silicon for Photovoltaic Applications , Vol. 85 (Springer, Berlin Heidelberg, 2005) Bulklifetime versus injection for a varying symmetry factor and energy level Fig. 1: Comparison of typical injection ranges of different measuring methods Fig. 2: injection dependent lifetime measurements on 2 different spots on a SiNx passivated mc-Si wafer Related Solutions and Industries: Epitaxial Layers & Thin Films Matching Products MDP series MDPmap Precision Lifetime Charachterization with Exceptional Sensitivity Learn more MDP series MDPspot Quick and Simple Lifetime Measurement Made Easy Learn more MDP series MDPpro 850+ Advanced Solution for Quality Control of Monocrystalline Silicon Ingots, Bricks, and Wafers Learn more MDP series MDPpro Advanced Lifetime Measurement System for Quality Control and Material R&D on Semiconductors Learn more Get in touch Do not hesitate to contact us – we are available to assist you with any inquiries or requests. Use our inquiry tool or reach out via email: sales @ freiberginstruments.com

Trap concentration determination Many lifetime measuring methods as QSSPC, µPCD or CDI, as well as MDP suffer from an anomalous high measured lifetime at very low injections. (Alttext kürzen, da zu lang) With the MDPmap and MDPingot it is possible to measure the photoconductivity as well as the minority carrier lifetime with one measurement and fully automated in a wide injection range. A clever algorithm allows the determination of the trap concentration in the sample. From the injection dependent lifetime curve the lifetime at low injection τ LLI can be determined and the photoconductivity is fitted with the slightly modified model of HORNBECK and HAYNES. The trapping density N T and the activation energy E A are the fitting parameters. First measurement results were obtained on mc- and Cz-Si wafers and a correlation between the trap density and the dislocation density could be confirmed. \(\Delta\delta = e[\tau_{LLI}G_{opt}(\mu_{n}+\mu_{p})+\Delta n_{T}\mu_{p}]\) MDPmap allows to measure injection dependent photoconductivity and lifetime curves with a high resolution, so that the trap density and activation energy of trapping centers can be determined. With this it is possible to investigate the origin of traps and there influence on for example the efficiency of solar cells. For more information read: [1] J. A. Hornbeck and J. R. Haynes, Physical Review 97, 311-321 (1955)[2] D. Macdonald and A. Cuevas, Applied Physics Letters 74, 1710 - 1712 (1999) [3] N. Schüler, T. Hahn, K. Dornich, J.R. Niklas, 25th PVSEC Valencia (2010) 343-346 Photoconductivity versus Gopt for different trap densities and fit of measured photoconductivity curve Related Solutions and Industries: Epitaxial Layers & Thin Films , Photovoltaic , Research and Development Matching Products MDP series MDPmap Precision Lifetime Charachterization with Exceptional Sensitivity Learn more MDP series MDPpro 850+ Advanced Solution for Quality Control of Monocrystalline Silicon Ingots, Bricks, and Wafers Learn more MDP series MDPpro Advanced Lifetime Measurement System for Quality Control and Material R&D on Semiconductors Learn more Get in touch Do not hesitate to contact us – we are available to assist you with any inquiries or requests. Use our inquiry tool or reach out via email: sales @ freiberginstruments.com

Detection of BO2 in silicon Boron-oxygen complexes are one of the main reasons why solar cells degrade, when irradiated with sun light. Hence it is important to measure the boron-oxygen density in silicon fast, destruction free and with a high resolution. The boron-oxygen complexes can be activated by irradiating the sample with light and deactivated by heating the sample at 200 °C for several minutes. This can be used similar to the iron determination, to determine the relative boron-oxygen density by lifetime measurements before and after the activation and deactivation of the defect complex. The boron-oxygen density is determined via: \([BO_{2}] = C_{BO}(\Delta n) \cdot (\cfrac{1}{\tau_{BO}} - \cfrac{1}{\tau_{FeB}})\) For the boron-oxygen determination a calibration factor CBO is used, which depends on the injection and doping concentration. With the MDPmap and the heated sample stage a determination of the boron-oxygen concentration is possible for mc- and mono-Si with a high resolution. Related Solutions and Industries: Epitaxial Layers & Thin Films Matching Products MDP series MDPmap Precision Lifetime Charachterization with Exceptional Sensitivity Learn more MDP series MDPpro 850+ Advanced Solution for Quality Control of Monocrystalline Silicon Ingots, Bricks, and Wafers Learn more MDP series MDPpro Advanced Lifetime Measurement System for Quality Control and Material R&D on Semiconductors Learn more Get in touch Do not hesitate to contact us – we are available to assist you with any inquiries or requests. Use our inquiry tool or reach out via email: sales @ freiberginstruments.com

Detection of CrB in silicon The determination of the chromium concentration is very important, since chromium is one of the most abundant and also most detrimental defects in silicon. (Alttext kürzen, da zu lang) Lifetime measurements before and after chromium boron pair dissociation is a widely used method for chromium determination in silicon wafers. In boron doped silicon with a high doping concentration, as it is used for PV applications nearly 100 % of the electrical active chromium is present as CrB pairs. With light of sufficient energy these pairs can be dissociated in Cri and B. This process is reversible and after some time all CrB pairs are associated again, which takes much longer as for FeB pairs. CrB and Cri have different recombination properties, so that the dissociation has an effect on the measured lifetime. With this effect the chromium concentration can be determined via: \([Cr] = C_{Cr}(\Delta n) \cdot (\cfrac{1}{\tau_{Cr}} - \cfrac{1}{\tau_{CrB}})\) For the chromium determination a calibration factor C is used, which depends on the injection and doping concentration. With the MDPmap and the heated sample stage a determination of the chromium concentration is possible for mc- and mono-Si with a high resolution. Related Solutions and Industries: Epitaxial Layers & Thin Films Matching Products MDP series MDPmap Precision Lifetime Charachterization with Exceptional Sensitivity Learn more MDP series MDPpro 850+ Advanced Solution for Quality Control of Monocrystalline Silicon Ingots, Bricks, and Wafers Learn more MDP series MDPpro Advanced Lifetime Measurement System for Quality Control and Material R&D on Semiconductors Learn more Get in touch Do not hesitate to contact us – we are available to assist you with any inquiries or requests. Use our inquiry tool or reach out via email: sales @ freiberginstruments.com

p/n detection in bricks Changes in the conduction type of a multicrystalline brick are frequently observed, due to a high phosphorus concentration in the low quality feedstock. (Alttext kürzen, da zu lang)) In the PV industry sometimes also low quality material with a high phosphorous concentration is used. Phosphor has a segregation coefficient of 0.35 and is therefore segregating in the top of the brick (last part that solidifies).There the concentration can be so high, that even changes in the conduction type from p to n can occur. Of course the n-type material cannot be used anymore for the solar cell production. Before the conduction type changes completely to n-conductivity, there is a narrow part of the ingot that is highly compensated and has a very high resistivity. Since resistivity measurements by eddy current are difficult to achieve in high resolution, it is preferable to use the photoconductivity for the detection of such a pn change. The photoconductivity or signal height depends on the resistivity because the skin depth of the microwave increases with increasing resistivity, so that at high resistivities a larger volume of the sample is measured. This dependency can be used for the pn detection. With a clever computer algorithm, it is possible to detect the sharp rise in photoconductivity, so that a pn-change can be detected with a resolution of 1 mm (fig.1 and fig.2). This algorithm can be implanted into the software of the MDPingot and MDPingot inline tool. The MDPingot and MDPingot inline allows to detect pn-changes inline with a resolution of 1mm as demonstrated in figure 1 and 2. With this feature useless n-material can be sorted out as early as possible in the production process. For more information please read: [1] N. Schüler, D. Mittelstrass, K. Dornich, J.R. Niklas, 35th IEEE Photovoltaic Specialists Conference Honululu, (2010) 852-857 Fig. 1: photoconductivity map of a mc-Si brick with the indicated detection brick height of the pn algorithm and height at which the mean resistivity linescan rises above 3 cm Fig. 2: mean photoconductivity linescan along with the output of the pn detection algorithm and the mean resistivity linescan Related Solutions and Industries: Epitaxial Layers & Thin Films Matching Products MDP series MDPpro 850+ Advanced Solution for Quality Control of Monocrystalline Silicon Ingots, Bricks, and Wafers Learn more MDP series MDPpro Advanced Lifetime Measurement System for Quality Control and Material R&D on Semiconductors Learn more Get in touch Do not hesitate to contact us – we are available to assist you with any inquiries or requests. Use our inquiry tool or reach out via email: sales @ freiberginstruments.com

Investigation of material quality of GaAs Besides silicon GaAs is one of the most important materials in modern technology and therefore a method to investigate the material quality is needed. (Alttext kürzen, da zu lang) In contrast to other techniques MD-PICTS (microwave detected photo induced current transient spectroscopy) can detect signals even from thin surface regions (3 µm) of SI GaAs samples and is therefore able to analyze e.g. influence of surface treatments. Figure 1 shows the defect peak of the well-known EL2 defect in samples with different acceptor concentrations. Fig. 1: Detection of the EL2 defect in SI GaAs samples with different acceptor concentrations by MD-PICTS, peak height and sign correlate to the acceptor concentration Related Solutions and Industries: Epitaxial Layers & Thin Films Matching Products MDP series MDPmap Precision Lifetime Charachterization with Exceptional Sensitivity Learn more MDP series MDPspot Quick and Simple Lifetime Measurement Made Easy Learn more MDP series MDpicts Temperature-Dependent Lifetime Measurement System for Advanced Material Analysis Learn more Get in touch Do not hesitate to contact us – we are available to assist you with any inquiries or requests. Use our inquiry tool or reach out via email: sales @ freiberginstruments.com

Minority carrier lifetime measurements on SiC In recent years the quality of SiC materials has improved profoundly and hence SiC is becoming more and more a competitor to Si for e.g. high-power devices. Since it is a wide-bandgap semiconductor, SiC has a number of advantages when compared to Si. The minority carrier lifetime is one of the fundamental parameters with regard to the performance of semiconductor devices, especially for the application of SiC in high voltage devices. Hence, it is necessary to perform lifetime engineering to gain the best performance of a certain device. In order to manufacture SiC devices with maximum yield, a material characterization with a high resolution is needed, together with a method to investigate the origin of defects in SiC to further improve the quality. The two contactless and destruction free methods microwave detected photoconductivity (MDP) and photo induced current transient spectroscopy (MD-PICTS) are ideal methods for material quality and defect characterization. The MDPmap combined with a UV-laser (355 nm) is the ideal tool for the spatial investigation of inhomogeneities in the minority carrier lifetime of SiC with a lower limit of 20 ns. MD-PICTS measurements enable the temperature dependent investigation of the photoconductivity transient allowing the determination of the defect activation energy and capture cross sections. With the MD-PICTS system it is possible to measure down to 85 K with a liquid nitrogen bath cryostat or even down to 4 K with a helium cooling system. The upper temperature limit is 800 K and hence also deep trap levels can be investigated. With the additional mapping option small samples (2 x 2 cm) can be mapped at different temperatures. Results Figure 1 and 2 show a minority carrier lifetime map and a photoconductivity transient of a 4H-SiC sample. Both was measured with the MDPmap with a resolution of 100 µm and a 355 nm laser. Figure 3 demonstrates a MD-PICTS spectrum with two detected defect levels with activation energies of 0.12 eV and 0.22 eV. The measurement was conducted with an MDpicts and a liquid nitrogen bath. For more information please read: B. Berger, N. Schüler, S. Anger, B. Gruendig-Wendrock, J. R. Niklas, K. Dornich, physica status solidi A, 1-8. Contactless electrical defectcharacterization in semiconductorsby microwave detected photo inducedcurrent transient spectroscopy (MD-PICTS) and microwave detected photoconductivity (MDP) Fig.1: Minority carrier lifetime map of a 4" SiC wafer Fig.2: Typical photoconductivity transient of a 4H-SiC sample Fig. 3: MD-PICTS spectrum of a 4H-SiC sample, with two trap levels Related Solutions and Industries: Epitaxial Layers & Thin Films Matching Products MDP series MDPmap Precision Lifetime Charachterization with Exceptional Sensitivity Learn more MDP series MDPspot Quick and Simple Lifetime Measurement Made Easy Learn more MDP series MDpicts Temperature-Dependent Lifetime Measurement System for Advanced Material Analysis Learn more Get in touch Do not hesitate to contact us – we are available to assist you with any inquiries or requests. Use our inquiry tool or reach out via email: sales @ freiberginstruments.com

Microwave Detected Photo Induced Current Transient Spectroscopy (MD-PICTS) is a modification of MDP, where temperature dependent measurements of the defect part of the transient are accomplished. In order to investigate defects in semiconductors it is widely spread to use temperature dependent methods as deep level transient spectroscopy (DLTS). Usually for these methods it is necessary to form contacts on the samples, which means the sample itself is often altered due to annealing steps. Furthermore for lot of semiconductors some effort is needed to create ohmic contacts at all. MD-PICTS is a non-destructive, contactless method with which the activation energies and capture cross sections of defects can be determined with a high accuracy. For MD-PICTS measurements the photoconductivity of a sample after the irradiation with light is measured with a resonant microwave cavity. For the determination of the activation energy the temperature dependent change of the photoconductivity transient is determined via a window analysis, which is also used for DLTS measurements (fig. 1). Fig.2 shows a so called MD-PICTS spectrum which results from the window analysis. Every peak in this spectrum is a certain defect in the sample. The temperature shift of the maximum of this peak is plotted in an Arrhenius plot according to this formula of the emission rate: \(e_{n} = \gamma\delta_{n}T^{2}e^{-\frac{E_{A}}{kT}}\) From the slope of the Arrhenius plot (Fig. 3) the activation energy can be determined. With the novel commercially available MD-PICTS equipment it is possible to measure the temperature dependence of the photoconductivity transient in a range from 20…500 K. In the past Si, GaAs, InP, SiC and many more semiconductors have already been successfully investigated with this method. For more information please read: [1] B. Berger, N. Schüler, S. Anger, B. Gruendig-Wendrock, J. R. Niklas, K. Dornich, physica status solidi A, 1-8 Fig. 1: Depiction of the window analysis of the photoconductivity transient Fig. 2: resulting MD-PICTS spectrum Fig. 3: Arrhenius plot Fig. 4: example of a MD-PICTS spectrum of different tempered Cz—Si wafers Related Solutions and Industries: Epitaxial Layers & Thin Films Matching Products MDP series HTpicts Advanced High-Temperature Lifetime Measurement System for In-Depth Material Analysis Learn more MDP series MDpicts pro High-Resolution, Temperature-Dependent Lifetime Measurement System for Precise Material Characterization Learn more MDP series MDpicts Temperature-Dependent Lifetime Measurement System for Advanced Material Analysis Learn more Get in touch Do not hesitate to contact us – we are available to assist you with any inquiries or requests. Use our inquiry tool or reach out via email: sales @ freiberginstruments.com

Iron concentration determination The exact determination of the iron concentration is very important, since iron is one of the most abundant and also most detrimental defects in silicon. (Alttext kürzen, da zu lang)) With the MDPingot and MDPmap series it is possible to measure the iron concentration in bricks and wafers fully automated and with a very high resolution. Lifetime measurements before and after iron boron pair dissociation is a widely used method for iron determination in silicon wafers. In boron doped silicon with a high doping concentration, as it is used for PV applications nearly 100 % of the electrical active iron is present as FeB pairs. With light of sufficient energy these pairs can be dissociated in Fe i and B. This process is reversible and after some time all FeB pairs are associated again. FeB and Fe i have different recombination properties, so that the dissociation has an effect on the measured lifetime. With this effect the iron concentration can be determined via: \([\mathrm{Fe}] = C(\Delta n) \cdot \left( \cfrac{1}{\tau_{\mathrm{Fe}_i}} - \cfrac{1}{\tau_{\mathrm{FeB}}} \right)\) For the iron determination a calibration factor C is used, which depends on the injection, doping concentration and trap concentration, which has to be considered especially in Multicrystalline silicon. With MDP a determination of the iron concentration is possible for mc- and mono-Si with a high resolution and thanks to simulations and years of research, also with a high accuracy. Lifetime map before illumination and resulting iron map Related Solutions and Industries: Epitaxial Layers & Thin Films , Photovoltaic , Research and Development Matching Products MDP series MDPpro 850+ Advanced Solution for Quality Control of Monocrystalline Silicon Ingots, Bricks, and Wafers Learn more MDP series MDPpro Advanced Lifetime Measurement System for Quality Control and Material R&D on Semiconductors Learn more MDP series MDPmap Precision Lifetime Charachterization with Exceptional Sensitivity Learn more Get in touch Do not hesitate to contact us – we are available to assist you with any inquiries or requests. Use our inquiry tool or reach out via email: sales @ freiberginstruments.com

Minority carrier Lifetime maps on 450 mm wafers Since several years, the microelectronic industry is planning to enlarge the wafer size from 300 mm (12 inch) to 450 mm (18 inch) diameter, in order to gain more yield. The technology for the production of such high-quality wafers is now available and only the cost issue of adapting the fabs is still prohibiting the transfer to a larger wafer size. These 450 mm wafers also need to be checked for extrinsic and intrinsic impurities and hence highly spatially resolved lifetime measurements are needed. In cooperation with Fraunhofer IISB , Freiberg Instruments developed a tool for the minority carrier lifetime measurement of 450 mm wafers in the EC-funded project SEA4KET . For the minority carrier lifetime measurement of 450 mm wafers basically the same measurement head as in the MDPmap and MDPpro is used with some adaption for the larger wafer size in the mapping part of the tool. Figure 1 shows one of the first measured lifetime maps of a 450 mm wafer, which clearly shows some handling traces and striations. In figure 2 and 3 the tool, which is situated in the clean room at Fraunhofer IISB is displayed. Fig. 1: minority carrier lifetime map of a 450 mm wafer Fig. 2: Versatile metrology module at Fraunhofer IISB site with implemented minority carrier lifetime measurement head (MDP sensor) in the course of feasibility evaluation activities within SEA4KET project. © Photo: Kurt Fuchs/Fraunhofer IISB Fig. 3: minority carrier lifetime measurement head (MDP sensor) and 450 mm wafer in the course of feasibility evaluation activities within SEA4KET project. © Photo: Kurt Fuchs/Fraunhofer IISB Related Solutions and Industries: Epitaxial Layers & Thin Films Matching Products MDP series MDPpro Advanced Lifetime Measurement System for Quality Control and Material R&D on Semiconductors Learn more MDP series MDPmap Precision Lifetime Charachterization with Exceptional Sensitivity Learn more Get in touch Do not hesitate to contact us – we are available to assist you with any inquiries or requests. Use our inquiry tool or reach out via email: sales @ freiberginstruments.com