Mechanism of Zn and Si diffusion from a highly doped tunnel junction for InGaP/GaAs tandem solar cells
Mechanism of Zn and Si diffusion from a highly doped tunnel junction for InGaP/GaAs tandem solar cells
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DOI：
10.1063/1.369278
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发表时间：
1999-02-01
影响因子：
3.2
通讯作者：
Al-Jassim, M
中科院分区：
文献类型：
--
作者：
Takamoto, T;Yumaguchi, M;Al-Jassim, M
本文研究了外延生长过程中杂质（Zn和Si）从隧道结中的扩散及其对InGaP/GaAs叠层电池性能的影响。已经发现从隧道结的Zn扩散恶化了背表面场层对InGaP顶部电池中的少数载流子反射率的影响，并且降低了顶部电池的量子效率。此外，已发现Zn扩散在GaAs衬底的穿透位错周围增强，并且仅在顶部单元区域中产生分流路径。当使用具有高蚀刻坑密度的不同衬底时，也观察到降低GaAs底部电池的量子效率的Si扩散。已经发现，通过使用夹在AlInP层之间的双异质结构InGaP隧道结，可以抑制Zn的这种异常扩散。已经发现，Zn扩散发生为在附近形成的高度掺杂有Si的层，并且Zn在与Si掺杂层相反的方向上扩散。Zn扩散被认为是由III族自扩散引起的，其起源于高度掺杂的n型层。Zn扩散的方向被认为是由于Ga位上的替位Zn和As位上的替位Si之间的库仑排斥。在AlInP势垒层和InGaP隧道结层中III族空位的形成和迁移的大能量被认为抑制了Zn从隧道结的扩散。(C)1999年美国物理学会。[S0021-8979（99）04203-6]。
Diffusion of impurities (Zn and Si) from a tunnel junction during epitaxial growth and the effects of impurity diffusion on InGaP/GaAs tandem cell properties have been investigated. Zn diffusion from the tunnel junction has been found to deteriorate the effect of the back-surface field layer on minority carrier reflectance in the InGaP top cell and degrade the quantum efficiency of the top cell. Furthermore, Zn diffusion has been found to be enhanced around the threading dislocations from a GaAs substrate and creates shunt paths only in the top cell region. Si diffusion, which degrades the quantum efficiency of the GaAs bottom cell, has also been observed when a different substrate with high etch pit density was used. Such anomalous diffusion of Zn has been found to be suppressed by using a double-hetero structure InGaP tunnel junction sandwiched by AlInP layers. It has been found that the Zn diffusion occurs as a layer highly doped with Si being formed nearby and Zn diffuses in the opposite direction from the Si-doped layer. The Zn diffusion is thought to be caused by group III self-diffusion which originates in the highly doped n-type layer. The direction of Zn diffusion is thought to be due to Coulombic repulsion between the substitutional Zn on the Ga site and the substitutional Si on the As site. The large energies of the formation and migration of group III vacancies in the AlInP barrier layers and InGaP tunnel junction layers are thought to suppress Zn diffusion from the tunnel junction. (C) 1999 American Institute of Physics. [S0021-8979(99)04203-6].