Abstract Tunnel layer passivated contact technology is already highly efficient in case of selective electron extraction but not as efficient in case of selective hole extraction. Thus far, SiOx/p+-poly-Si contacts have resulted only in efficiencies above ~20.1% for rear-side deployed hole selective contacts. We investigate if hole extraction selectivity can be further improved by substituting the ‘conventionally’ used SiOx tunnel layer exhibiting moderate or even high positive fixed charge density by AlOx tunnel layers, exhibiting high negative fixed charge density. The merits of using atomic layer deposited ultrathin AlOx tunnel layers are investigated and compared with wet chemically formed SiOx tunnel layers to form AlOx/p+-poly-Si and SiOx/p+-poly-Si hole selective passivated contacts respectively. The AlOx thickness (0.13–2 nm) and its thermal budget including annealing time, temperature and ambient were varied. The quality of the resulting AlOx/p+-poly-Si passivated contacts was determined by measuring the recombination current density (Jc) and the effective contact resistivity (ρc). Finally, using the measured values of Jc and ρc, we predict the efficiency potential and selectivity of the passivated contact using Brendel's model. We show that for 425 °C annealed AlOx samples prior to poly-Si capping, there is an improvement in passivation quality due to the high negative AlOx interface charge, which forms only for “thick” tunnel layers (≥1.5 nm). However, after high-temperature poly-Si capping, enhanced boron in-diffusion and charge compensation are degrading the overall passivation quality of “thick” AlOx/p+-poly-Si passivated contacts. The best AlOx/p+-poly-Si passivated contacts use ultra-thin AlOx tunnel layers (efficiency potential of 26.9%), which is only marginally better than the SiOx reference samples, but still improves hole selectivity.

中文翻译：

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用于高效太阳能电池的工程氧化铝/多晶硅空穴选择性钝化触点

摘要 隧道层钝化接触技术在选择性电子提取的情况下已经非常高效，但在选择性空穴提取的情况下效率不高。到目前为止，SiOx/p+-poly-Si 接触仅导致背面部署的孔选择性接触的效率高于约 20.1%。我们研究了是否可以通过用 AlOx 隧道层代替“常规”使用的具有中等甚至高正固定电荷密度的 SiOx 隧道层来进一步提高空穴提取选择性，表现出高负固定电荷密度。研究了使用原子层沉积超薄 AlOx 隧道层的优点，并与湿法化学形成的 SiOx 隧道层进行比较，以分别形成 AlOx/p+-poly-Si 和 SiOx/p+-poly-Si 空穴选择性钝化接触。AlOx 厚度 (0. 13-2 nm）及其热预算，包括退火时间、温度和环境。通过测量复合电流密度 (Jc) 和有效接触电阻率 (ρc) 来确定所得 AlOx/p+-poly-Si 钝化触点的质量。最后，使用 Jc 和 ρc 的测量值，我们使用 Brendel 模型预测钝化接触的效率潜力和选择性。我们表明，对于多晶硅封盖之前的 425°C 退火的 AlOx 样品，由于高负的 AlOx 界面电荷，钝化质量有所提高，这仅在“厚”隧道层（≥1.5 nm）时形成。然而，在高温多晶硅封盖后，增强的硼扩散和电荷补偿正在降低“厚”AlOx/p+-多晶硅钝化触点的整体钝化质量。