Abstract:The thermal and ultraviolet (UV) stability of crystalline silicon (c-Si) surface passivation provided by atomic layer deposited Al2O3 was compared with results for thermal SiO2. For Al2O3 and Al2O3/a-SiNx:H stacks on 2 Ω cm n-type c-Si, ultralow surface recombination velocities of Seff<3 cm/s were obtained and the passivation proved sufficiently stable (Seff<14 cm/s) against a high temperature “firing” process (>800 °C) used for screen printed c-Si solar cells. Effusion measurements reveal… Show more
“…The trends of the Si PL signal and S eff were qualitatively in good agreement: S eff decreased by annealing at moderate temperatures, whereas higher temperatures led to a degradation of the passivation performance. 29,37 The effective lifetime of $ 6 ls measured after annealing at 1000 C was similar to that obtained for an unpassivated Si …”
Section: Si Luminescence and Surface Passivationsupporting
confidence: 72%
“…Note that the presence of a significant density of CO x groups in the bulk of the material would also not be expected for ALD with H 2 O as the oxidant, in contrast to plasma ALD where C-O vibrations were detected by infrared absorption spectroscopy. 33,37,42 On the other hand, it is likely that the CH x feature at 740 C can be attributed to the removal of carbon impurities that originate from the precursor and were incorporated into the Al 2 O 3 :Er film during deposition. Maxima in the effusion transients were observed at 700 C for both H 2 O and H 2 .…”
Section: Effect Of Annealing On Structural Propertiesmentioning
Atomic layer deposition was used to deposit amorphous Er-doped Al2O3 films (0.9–6.2 at. % Er) on Si(100). The Er3+ photoluminescence (PL), Er3+ upconversion luminescence, as well as the Si PL and associated surface passivation properties of the films were studied and related to the structural change of the material during annealing. The PL signals from Er3+ and Si were strongly dependent on the annealing temperature (T = 450–1000 °C), but not directly influenced by the transition from an amorphous to a crystalline phase at T > 900 °C. For T > 650 °C, broad Er3+ PL centered at 1.54 μm (4I13/2) with a full width at half maximum of 55 nm was observed under excitation of 532 nm light. The PL signal reached a maximum for Er concentrations in the range of 2–3 at. %. Multiple photon upconversion luminescence was detected at 660 nm (4F9/2), 810 nm (4I9/2), and 980 nm (4I11/2), under excitation of 1480 nm light. The optical activation of Er3+ was related to the removal of quenching impurities, such as OH (3 at. % H present initially) as also indicated by thermal effusion experiments. In contrast to the Er3+ PL signal, the Si luminescence, and consequently the Si surface passivation, decreased for increasing annealing temperatures. This trade-off between surface passivation quality and Er3+ PL can be attributed to an opposite correlation with the decreasing hydrogen content in the films during thermal treatment.
“…The trends of the Si PL signal and S eff were qualitatively in good agreement: S eff decreased by annealing at moderate temperatures, whereas higher temperatures led to a degradation of the passivation performance. 29,37 The effective lifetime of $ 6 ls measured after annealing at 1000 C was similar to that obtained for an unpassivated Si …”
Section: Si Luminescence and Surface Passivationsupporting
confidence: 72%
“…Note that the presence of a significant density of CO x groups in the bulk of the material would also not be expected for ALD with H 2 O as the oxidant, in contrast to plasma ALD where C-O vibrations were detected by infrared absorption spectroscopy. 33,37,42 On the other hand, it is likely that the CH x feature at 740 C can be attributed to the removal of carbon impurities that originate from the precursor and were incorporated into the Al 2 O 3 :Er film during deposition. Maxima in the effusion transients were observed at 700 C for both H 2 O and H 2 .…”
Section: Effect Of Annealing On Structural Propertiesmentioning
Atomic layer deposition was used to deposit amorphous Er-doped Al2O3 films (0.9–6.2 at. % Er) on Si(100). The Er3+ photoluminescence (PL), Er3+ upconversion luminescence, as well as the Si PL and associated surface passivation properties of the films were studied and related to the structural change of the material during annealing. The PL signals from Er3+ and Si were strongly dependent on the annealing temperature (T = 450–1000 °C), but not directly influenced by the transition from an amorphous to a crystalline phase at T > 900 °C. For T > 650 °C, broad Er3+ PL centered at 1.54 μm (4I13/2) with a full width at half maximum of 55 nm was observed under excitation of 532 nm light. The PL signal reached a maximum for Er concentrations in the range of 2–3 at. %. Multiple photon upconversion luminescence was detected at 660 nm (4F9/2), 810 nm (4I9/2), and 980 nm (4I11/2), under excitation of 1480 nm light. The optical activation of Er3+ was related to the removal of quenching impurities, such as OH (3 at. % H present initially) as also indicated by thermal effusion experiments. In contrast to the Er3+ PL signal, the Si luminescence, and consequently the Si surface passivation, decreased for increasing annealing temperatures. This trade-off between surface passivation quality and Er3+ PL can be attributed to an opposite correlation with the decreasing hydrogen content in the films during thermal treatment.
“…These results are comparable to the solar cells employing thermal oxide as used in record-efficiency solar cells [39]. Al 2 O 3 layer also demonstrated a better UV stability than thermal SiO 2 with the surface passivation improving during UV irradiation [41].…”
“…Al 2 O 3 film grown by atomic layer deposition (ALD) has demonstrated excellent uniformity and growth control, suggesting better passivation quality [1]. Al 2 O 3 synthesized by ALD provides a high quality surface because its low interface state density provides good chemical passivation and the negative fixed charges near the interface for p-type c-Si provide excellent field-effect passivation [2][3][4][5][6]. Al 2 O 3 film also can offer excellent dielectric properties [7].…”
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