Search

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. [ABSTRACT FROM AUTHOR]

Surface‐related degradation (SRD) is a phenomenon whereby recombination in the near‐surface region of silicon wafers increases under elevated temperatures with or without carrier injection. Because of its importance for solar cell processing and operation, SRD occurring under light soaking at temperatures between 80 and 200 °C has recently attracted great interest. In this work, two post‐firing processes that can affect the formation of SRD are investigated. The first is the replacement of the passivating dielectric layers and the second is the use of thermal annealing between 300 and 400 °C. Post‐firing etching and redeposition of dielectric layers have minimal impact on subsequent degradation. In contrast, a thermal anneal at 400 °C for 30 min can reduce the extent of SRD by a factor of 6. These results imply that the interface between silicon and the dielectric itself is not the critical factor in the formation of SRD. The most likely explanation is that thermal processing causes an alteration in the silicon substrate that affects the subsequent formation of SRD. [ABSTRACT FROM AUTHOR]

At present, the commercially dominant and rapidly expanding PV‐device technology is based on the passivated emitter and rear cell (PERC) design developed at UNSW. However, this technology has been found to suffer from a carrier‐induced degradation commonly referred to as 'light‐ and elevated temperature‐induced degradation' (LeTID) and can result in up to 16% relative performance losses. LeTID was recently shown to occur in almost every type of silicon wafer, independent of the doping material. Even though the degradation mechanism is known to recover under normal operation conditions, it is a lengthy process that drastically affects the energy yield, stability and, ultimately, the levelized cost of electricity (LCOE) of installed systems. Despite the joint effort of many research groups, the root cause of the degradation is still unknown. Here, we provide an overview of the existing literature and describe key LeTID characteristics and how these have led to the development of various theories of the underlying mechanism. Further, given the continuously appearing and strong evidence of hydrogen involvement in LeTID, many mitigation methods concerning hydrogenation have been suggested. We discuss such reported methods, bearing in mind crucial consumer necessities in terms of sustained cell performance and minimised LCOE. [ABSTRACT FROM AUTHOR]

Hydrogen passivation is a key industrial technique used to reduce the recombination activity of defects in multicrystalline silicon (mc‐Si). However, not all dislocations and grain boundaries respond well to traditional hydrogen passivation techniques. In order to understand the reasons for these different behaviours, and how superior passivation might be achieved, a method is required for the direct observation of hydrogen at these defects. Here, we present a novel characterisation technique based on a combination of transmission Kikuchi diffraction (TKD), atom probe tomography (APT), and isotopic substitution that enables unambiguous detection and quantification of hydrogen atoms present at crystallographic defects in mc‐Si. [ABSTRACT FROM AUTHOR]