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首页> 外文会议>Transparent Optical Networks, 2003. Proceedings of 2003 5th International Conference on >Physics and design of low noise avalanche photodiodes - LEOS distinguished lecture 2003-2004
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Physics and design of low noise avalanche photodiodes - LEOS distinguished lecture 2003-2004

机译：低噪声雪崩光电二极管的物理与设计-LEOS杰出演讲2003-2004

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Summary form only given. Avalanche photodiodes (APDs) are used in many applications when conventional unity gain photodiodes cannot provide enough sensitivity and the extra amplification provided by the impact ionization process gives it an advantage. Unfortunately this amplification or gain of the incoming optical signal is always accompanied by some 'excess noise' due to the stochastic nature of the ionization process and this sets a limit to the maximum useful gain. Early work by McIntyre showed that the excess noise depended on the ratio of hole ionization coefficient (/spl beta/) to electron ionization coefficient (/spl alpha/). /spl alpha/ and /spl beta/ are semiconductor material dependent and unfortunately most III-V materials have /spl alpha//spl ap//spl beta/, giving rise to relatively high excess noise. Since the ionization coefficients depend on the details of the band structure it is extremely difficult to modify, even using band-gap engineering techniques such as superlattices or MQWs. In recent years, work done at the University of Sheffield and the University of Texas (Austin) has shown that low excess noise can be obtained in homojunction structures simply by utilising thin avalanching regions. Experimental results show that contrary to conventional theory, the excess noise actually decreases as the avalanching width reduces. This behaviour has now been observed in virtually all semiconductor materials including GaAs, AlGaAs, InP, AlInAs and even silicon. The reason for this anomalous behaviour in thin devices is due to the 'dead space' (d), defined as the minimum distance a carrier has to travel before it is in equilibrium with the electric field. Conventional models of the ionization process ignored. This assumption is generally valid in devices with thick avalanching widths in which the dead space distance, d, is relatively small compared to the avalanching width, w. In thin avalanching width structures, d becomes a significant fraction of w and the ionizing process becomes more deterministic, reducing the stochastic variations that give rise to the excess noise. This talk will review these results and show that in addition to reducing the excess noise, thin avalanching widths offer APDs with other advantages such as lower operating voltages, better temperature stability and predicted enhanced speed of operation.
机译：仅提供摘要表格。当常规的单位增益光电二极管无法提供足够的灵敏度，并且碰撞电离过程提供的额外放大使其具有优势时，雪崩光电二极管（APD）可用于许多应用。不幸的是，由于电离过程的随机性，入射光信号的这种放大或增益总是伴随着一些“多余的噪声”，这限制了最大有用增益。 McIntyre的早期工作表明，多余的噪声取决于空穴电离系数（/ spl beta /）与电子电离系数（/ spl alpha /）之比。 / spl alpha /和/ spl beta /是半导体材料依赖的，不幸的是，大多数III-V材料具有/ spl alpha // spl ap // spl beta /，从而产生了相对较高的过量噪声。由于电离系数取决于能带结构的细节，因此即使使用带隙工程技术（例如超晶格或MQW），也很难对其进行修改。近年来，在谢菲尔德大学和德克萨斯大学（奥斯汀）所做的工作表明，仅通过利用薄薄的雪崩区域，就可以在同质结结构中获得较低的多余噪声。实验结果表明，与传统理论相反，过量噪声实际上随着雪崩宽度的减小而减小。现在几乎在所有半导体材料中都观察到了这种行为，包括GaAs，AlGaAs，InP，AlInAs甚至硅。薄型设备中这种异常行为的原因是由于“死区”（d），死区定义为载流子在与电场达到平衡之前必须经过的最小距离。电离过程的常规模型被忽略。该假设通常在具有较厚雪崩宽度的器件中有效，其中死空间距离d与雪崩宽度w相比相对较小。在薄的雪崩宽度结构中，d占w的很大一部分，电离过程变得更加确定性，从而减少了产生过多噪声的随机变化。本演讲将回顾这些结果，并表明，除了减少多余的噪声外，较薄的雪崩宽度还为APD提供了其他优势，例如更低的工作电压，更好的温度稳定性以及预计的提高的工作速度。

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