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This work compares the firing response of ex‐situ doped p‐ and n‐type polysilicon (poly‐Si) passivating contacts and identifies possible mechanisms underlying their distinct firing behavior. The p‐type poly‐Si shows greater firing stability than n‐type poly‐Si, particularly at a higher firing temperature, which results in a substantial increase in the recombination current density parameter J0 from 9 to 96 fA/cm2 upon firing at 900°C for n‐type poly‐Si, in comparison to an increase from 11 to 30 fA/cm2 for p‐type poly‐Si. It is observed that p‐type poly‐Si contacts only suffer a slight degradation or even exhibit a small improvement in J0 after firing at 800°C, depending on the boron diffusion temperature. Secondary ion mass spectrometry (SIMS) results demonstrate that the hydrogen concentration near the interfacial SiOx increases with the peak firing temperature in n‐type poly‐Si, whereas the hydrogen profile remains unchanged for p‐type poly‐Si upon firing at various temperatures. Moreover, we observe that injecting additional hydrogen into the poly‐Si/SiOx stacks fired with SiNx coating layers further degrades n‐type poly‐Si, but recovers the J0 of p‐type poly‐Si to the value before firing. In contrast, removing hydrogen from the fired poly‐Si/SiOx stacks leads to an initial recovery and then a second degradation of J0 in n‐type poly‐Si, but no substantial impact on p‐type poly‐Si. It is hypothesized that the distinct difference in the firing impact on p‐ and n‐type poly‐Si is related to the different effective hydrogen diffusivity, which determines the hydrogen content surrounding the SiOx layer and hence the passivation quality after firing. [ABSTRACT FROM AUTHOR]

Photoluminescence (PL) images and micro-PL maps were taken on Cu- or Ni-doped monocrystalline silicon wafers, to investigate the distribution of the metal precipitates. Several n-type and p-type wafers were used in which Cu or Ni were introduced in the starting melt of the ingots and precipitated during the ingot cooling (as opposed to surface contamination). The micro-PL mapping allowed investigation of the metal precipitates with a higher spatial resolution. Markedly different precipitation patterns were observed in n- and p-type samples: in both Cu- and Ni-doped n-type samples, circular central regions and edge regions were observed. In these regions, particles were distributed randomly and homogeneously. In the p-type Cu-doped and Ni-doped samples, by contrast, the precipitates occurred in lines along <110> orientations. The difference in the precipitation behaviour in n- and p-type samples is conjectured to be caused by different concentrations of self-interstitials and vacancies remaining in the crystal during the ingot cooling: there are more vacancies in the n-type ingots but more interstitials in the p-type ingots. The dopant effects on the intrinsic point defect concentrations in silicon crystals and possible precipitation mechanisms are discussed based on the findings in this work and the literature. [ABSTRACT FROM AUTHOR]

We present a systematic investigation of the effects of doping on the luminescence spectra from p-type crystalline silicon wafers. First, we explain the difference in the approaches between the line shape analysis and the generalized Planck’s law in modeling the spectral shape, and connect the two methods together. After that, we elucidate the separate impacts of individual phenomena including band gap narrowing, band tails and dopant bands, Fermi level shifting, and hot carriers on the luminescence spectra in heavily-doped silicon. Finally, employing appropriate excitation levels, we can unambiguously re-examine the growing of the band tails and the broadening of the shallow dopant band, as well as the merging of the valence and shallow dopant bands together, on measured luminescence spectra. [ABSTRACT FROM AUTHOR]

Photoluminescence spectroscopy at 79 K is shown to provide an alternative, non-destructive characterisation method for quantifying the boron and phosphorous dopant concentrations in silicon. The dopant concentrations are revealed by the photoluminescence intensity ratios of the dopant-related features to the band-to-band recombination peaks. The intensity ratio is found to be insensitive to the excitation power in a wide range of 0.3 W cm−2-100 kW cm−2. Calibration curves for boron and phosphorous in silicon are presented for [B] below 5 × 1017 cm−3 and [P] below 8 × 1016 cm−3. [ABSTRACT FROM AUTHOR]

This paper presents findings on applying physical models in the literature to describe silicon luminescence spectra at 80 – 300 K. Incorporation of exciton recombination models are shown to disagree with the measured luminescence spectra, whereas a free electron-hole recombination model is shown to match well with the luminescence spectra. However, the lack of consideration for excitons is not justified, as Bludau et al. [ J. Appl. Phys. , vol. 45, p. 1846, 1974] reported that excitons are present even at room temperature. The second part of the paper demonstrates the impact of shallow dopants on the silicon luminescence spectra at 79K. The ratio of the dopant-related peak to the band-to-band peak intensities correlates with the dopant concentration, indicating that luminescence spectroscopy has the potential for quantifying dopant concentrations in silicon in this temperature range. [ABSTRACT FROM AUTHOR]

We report and explain the photoluminescence spectra emitted from silicon solar cells with heavily-doped layers at the surface. A micro-photoluminescence spectroscopy system is employed to investigate the total spectrum emitted from both the heavily-doped layer and the silicon substrate with micron-scale spatial resolution. The two regions of the device give rise to separate photoluminescence peaks, due to band-gap narrowing effects in the highly-doped layer. Two key parameters, the absorption depth of the excitation wavelength, and the sample temperature, are shown to be critical to reveal the separate signatures from the two regions. Finally, this technique is applied to locally diffused and laser-doped regions on silicon solar cell pre-cursors, demonstrating the potential value of this micron-scale technique in studying and optimizing locally doped regions. (© 2015 WILEY-VCH Verlag GmbH &Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]