Pure boron (PureB) deposition as the anode region of Si photodiodes creates negative fixed charge at the boron/silicon interface, which is responsible for effective suppression of electron injection from the bulk, thus ensuring low saturation/dark current densities. This mechanism is shown here to remain effective when PureB diodes, fabricated at 700 °C, are operated at cryogenic temperatures down to 100 K. Although the PureB junctions were only a few nanometers deep, they displayed the same current–voltage ( ${I}$ – ${V}$ ) characteristics as conventional deep diffused p ⁺ -n junction diodes in the whole temperature range and also maintained ideality factors close to ${n} = 1$ . Al-contacting was found to reveal process-related defects in the form of anomalous high current regions giving kinks in the ${I}$ – ${V}$ characteristics, often only visible at low temperatures. They were identified as minute Al–Si Schottky junctions with an effective barrier height of ~0.65 ± 0.05 eV. In PureB single-photon avalanche diodes (SPADs), Al–Si perimeter defects appeared but did not affect the breakdown voltage characteristics set by implicit guard rings. Low series resistance required thin B-layers that promoted tunneling. In particular, for such thin layers, avoiding Al-related degradation puts stringent requirements on wafer cleaning and window etch procedures.

中文翻译：

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PureB光电二极管的低温电性能揭示了铝金属化相关的暗电流降解

作为Si光电二极管的阳极区域的纯硼（PureB）沉积在硼/硅界面处产生负的固定电荷，这可有效抑制来自主体的电子注入，从而确保低饱和/暗电流密度。当在700°C的温度下制造的PureB二极管在低至100 K的低温下工作时，此机制仍然有效。尽管PureB结的深度只有几纳米，但它们显示出相同的电流-电压（ $ {I} $ – $ {V} $ ）特性 在整个温度范围内具有常规的深扩散p ⁺ -n结二极管的特性，并且还保持了接近于 $ {n} = 1 $ 。铝接触被发现以异常高电流区域的形式揭示了与工艺相关的缺陷，从而在电极上产生扭结。 $ {I} $ – $ {V} $ 特性，通常仅在低温下可见。它们被确定为具有有效势垒高度〜0.65±0.05 eV的微小Al-Si肖特基结。在PureB单光子雪崩二极管（SPAD）中，出现了Al-Si周边缺陷，但并未影响由隐式保护环设置的击穿电压特性。低串联电阻需要促进隧道效应的薄B层。特别地，对于这样的薄层，避免铝相关的降解对晶片清洁和窗口蚀刻程序提出了严格的要求。