Peter Wilshaw

© 2020 Author(s). In this paper, the physical mechanisms involved in electron-beam-induced current (EBIC) imaging of semiconductor pn-junctions are reviewed to propose a model and optimize the acquisition of experimental data. Insights are drawn on the dependence of the EBIC signal with electron accelerating voltage and surface conditions. It is concluded that improvements in the resolution of EBIC are possible when the surface conditions of the specimens are carefully considered and optimized. A lower accelerating voltage and an increase of the surface recombination velocities are quantitatively shown to maximize the EBIC lateral resolution in locating the pn-junction. The effect of surface band bending is included in the model, and it is seen to primarily affect the surface recombination. Introducing controlled surface damage is shown as a potential method for resolution enhancement via focused ion beam milling with Ga+ ions. These findings contribute to the understanding of this technique and can produce further improvements to its application in semiconductor device technology.

© 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim Silicon wafers for photovoltaics could be produced without kerf loss by rolling, provided sufficient control of defects such as dislocations can be achieved. A study using mainly high resolution electron backscatter diffraction (HR-EBSD) of the microstructural evolution of Siemens polycrystalline silicon feedstock during a series of processes designed to mimic high temperature rolling is reported here. The starting material is heavily textured and annealing at 1400 °C results in 90% recrystallization and a reduction in average geometrically necessary dislocation (GND) density from >1014 to 1013 m−2. Subsequent compression at 1150 °C – analogous to rolling – produce sub-grain boundaries seen as continuous curved high GND content linear features spanning grain interiors. Post-deformation annealing at 1400 °C facilitates a secondary recrystallization process, resulting in large grains typically of 100 μm diameter. HR-EBSD gives the final average GND density in as 3.2 × 1012 m−2. This value is considerably higher than the dislocation density of 5 × 1010 m−2 from etch pit counting, so the discrepancy is investigated by direct comparison of GND maps and etch pit patterns. The GND map from HR-EBSD gives erroneously high values at the method's noise floor (≈1012 m−2) in regions with low dislocation densities.

© 2018 IEEE. This paper presents a simple method of studying the transport of hydrogen in crystalline silicon, as well as its release from bound forms during annealing at temperatures between 350-450°C. This technique is based upon observations of an increase in the contact resistance of industrial solar cells, which displays the reversibility and dependence upon electric field commonly associated with hydrogen. It is shown that the increase in contact resistance depends strongly upon whether the device is fabricated on multi-or mono-crystalline silicon and upon the device structure.