Model for a-Si:H/c-Si interface recombination based on the amphoteric nature of silicon dangling bonds
Model for a-Si:H/c-Si interface recombination based on the amphoteric nature of silicon dangling bonds
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DOI：
10.1103/physrevb.76.035326
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发表时间：
2007-07-01
影响因子：
3.7
通讯作者：
Ballif, Christophe
中科院分区：
文献类型：
--
作者：
Olibet, Sara;Vallat-Sauvain, Evelyne;Ballif, Christophe
许多硅器件的性能受到晶体硅（c-Si）表面的电子复合损耗的限制。需要适当的表面钝化方案以使这些损失最小化。本文研究了非晶硅（a-Si：H）在单晶硅上的表面钝化特性。我们介绍了一个简单的模型，通过两性缺陷，即悬挂键，已经建立了体a-Si：H的表面复合机制的基础上的复合的描述。在这个模型中，在a-Si：H/c-Si界面的注入依赖的复合由两性复合中心的密度和平均电荷状态决定。我们表明，与我们的表面复合模型，我们可以区分两个主要机制的各自的贡献，导致改善表面钝化，这是通过（a）的复合中心的密度最小化和（B）的强烈减少的密度的一个载流子类型的界面附近的场效应。此后，我们可以再现实验观察到的不同晶片上的表面复合对注入水平的依赖性的行为，即，P和N掺杂类型以及本征的。最后，我们能够利用我们的a-Si：H层的良好表面钝化性能，制造开路电压超过700 mV的平面异质结太阳能电池。
The performance of many silicon devices is limited by electronic recombination losses at the crystalline silicon (c-Si) surface. A proper surface passivation scheme is needed to allow minimizing these losses. The surface passivation properties of amorphous hydrogenated silicon (a-Si:H) on monocrystalline Si wafers are investigated here. We introduce a simple model for the description of the surface recombination mechanism based on recombination through amphoteric defects, i.e. dangling bonds, already established for bulk a-Si:H. In this model, the injection-dependent recombination at the a-Si:H/c-Si interface is governed by the density and the average state of charge of the amphoteric recombination centers. We show that with our surface recombination model, we can discriminate between the respective contribution of the two main mechanisms leading to improved surface passivation, which is achieved by (a) the minimization of the density of recombination centers and (b) the strong reduction of the density of one carrier type near the interface by field effect. We can thereafter reproduce the behaviors experimentally observed for the dependence of the surface recombination on the injection level on different wafers, i.e., of both p and n doping type as well as intrinsic. Finally, we are able to exploit the good surface passivation properties of our a-Si:H layers by fabricating flat heterojunction solar cells with open-circuit voltages exceeding 700 mV.