Advanced modeling of the effective minority carrier lifetime of passivated crystalline silicon wafers

Abstract

Articles you may be interested inThe effect of light soaking on crystalline silicon surface passivation by atomic layer deposited Al2O3 J. Appl. Phys. 113, 024509 (2013); 10.1063/1.4775595 Minority charge carrier lifetime mapping of crystalline silicon wafers by time-resolved photoluminescence imaging J. Appl. Phys. 110, 054508 (2011); 10.1063/1.3630031 High effective minority carrier lifetime on silicon substrates using quinhydrone-methanol passivation Appl. Phys. Lett. 96, 063502 (2010); 10.1063/1.3309595 Impact of metal-oxide gate dielectric on minority carrier lifetime in siliconA strong injection level dependence of the effective minority carrier lifetime (s eff ) is typically measured at low injection levels for undiffused crystalline silicon (c-Si) wafers symmetrically passivated by a highly charged dielectric film. However, this phenomenon is not yet well understood. In this work, we concentrate on two of those possible physical mechanisms to reproduce measured s eff data of c-Si wafers symmetrically passivated by atomic layer deposited Al 2 O 3 . The first assumes the existence of a defective region close to the c-Si surface. The second assumes asymmetric electron and hole lifetimes in the bulk. Both explanations result in an adequate reproduction of the injection dependent s eff found for both n-and p-type c-Si wafers. However, modeling also predicts a distinctly different injection dependence of s eff for the two suggested mechanisms if the polarity of the effective surface charge is inverted. We test this prediction by experimentally inverting the polarity of the effective surface charge using corona charges. From the experiments and simulations, it is concluded that surface damage is the most likely cause of the significant reduction of s eff at low injection levels. V C 2012 American Institute of Physics. [http://dx.

On the c-Si/SiO2 interface recombination parameters from photo-conductance decay measurements

“…Several reports have addressed this discrepancy by proposing an enhanced recombination region near the surface, the so-called surface damage region, yet this hypothesis remains unsupported by direct experimental evidence. [22][23][24] Multiple modelling studies have followed those of Girisch and Aberle. Dauwe et al 25 and Weber et al, 26 for example, modelled SRV or (equivalently) dark saturation current J 0e for a single value of minority carrier injection and varied the dielectric charge concentration.…”

Proof-of-concept framework to separate recombination processes in thin silicon wafers using transient free-carrier absorption spectroscopy

“…In reality, surface recombination is complicated due to the presence of fixed charges and a distribution of interface trap states. 35 Previous works have also shown that the injection dependence of S eff for silicon nitride 36 and silicon oxide 37 passivation is sensitive to the base doping of Si. A more accurate treatment of surface recombination involves taking into account these phenomena.…”

“…A more accurate treatment of surface recombination involves taking into account these phenomena. 35 In addition, we assume a single mid-gap defect in the bulk with equal electron and hole time constants (s n0 ¼ s p0 ), which reduces the number of fitting parameters. However, defects can have asymmetric s n0 and s p0 that will cause SRH recombination to exhibit strong injection dependence.…”

Assessing the Performance of Surface Passivation Using Low-Intensity Photoluminescence Characterization Techniques

“…When the silicon is passivated by a layer which induces accumulation conditions at the surface, this effect is not seen as there is no point where the electron and hole concentrations are approximately equal. Ma et al simulated two possible causes of the observed injection dependence: 1) the asymmetric electron and hole lifetimes in the bulk, and 2) the SDR of which they identify the latter to be the most likely cause [16]. Throughout all of these works, it is not always clear if parasitic recombination that is present outside of the measured area has been accounted for before analyzing the results.…”

“…This has severe implications for solar cells with undiffused p-type surfaces passivated by SiN x and n-type surfaces passivated by Al 2 O 3 , as their performance will deteriorate under low illumination. Numerous theories have been presented to explain this effect [6]- [8], [11]- [16]. For example, it has been suggested that the degradation in lifetime at low injection levels is due to high asymmetry of the charged and neutral capture cross sections of the defects at the SiN x /Si interface, causing an increased surface recombination velocity at low injection [6], although no evidence of this has been observed experimentally [7].…”