Impact of Individual Structural Defects in GaAs Solar Cells: A Correlative and In Operando Investigation of Signatures, Structures, and Effects

Chen, Qiong; McKeon, Brandon S.; Zhang, Sunny Y.; Zhang, Fan; Hu, Changkui; Gfroerer, T. H.; Wanlass, M. W.; Smith, David J.; Yong, Zhang

doi:10.1002/adom.202001487

Cited by 9 publications

(3 citation statements)

References 31 publications

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“…We note that the lateral extensions of the defects identified in these epitaxially-grown solar cells are much smaller than the dislocation defects observed in GaAs ingots, which are intended to be used as substrates, with lateral sizes in the order of 100 μm [30,31] . Moreover, dislocation defects originated from the substrate, e.g., in SiC [19] , are often found to be much larger in lateral size.…”

Section: Correlative Structural Characterization Of Individual Defectsmentioning

confidence: 99%

Comprehensive,in operando, and correlative investigation of defects and their impact on device performance

Zhang¹,

Smith²

2022

J. Semicond.

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Despite the long history of research that has focused on the role of defects on device performance, the studies have not always been fruitful. A major reason is because these defect studies have typically been conducted in a parallel mode wherein the semiconductor wafer was divided into multiple pieces for separate optical and structural characterization, as well as device fabrication and evaluation. The major limitation of this approach was that either the defect being investigated by structural characterization techniques was not the same defect that was affecting the device performance or else the defect was not characterized under normal device operating conditions. In this review, we describe a more comprehensive approach to defect study, namely a series mode, using an array of spatially-resolved optical, electrical, and structural characterization techniques, all at the individual defect level but applied sequentially on a fabricated device. This novel sequential approach enables definitive answers to key questions, such as: (i) how do individual defects affect device performance? (ii) how does the impact depend on the device operation conditions? (iii) how does the impact vary from one defect to another? Implementation of this different approach is illustrated by the study of individual threading dislocation defects in GaAs solar cells. Additionally, we briefly describe a 3-D Raman thermometry method that can also be used for investigating the roles of defects in high power devices and device failure mechanisms.

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Section: Correlative Structural Characterization Of Individual Defectsmentioning

confidence: 99%

Comprehensive,in operando, and correlative investigation of defects and their impact on device performance

Zhang¹,

Smith²

2022

J. Semicond.

Self Cite

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“…It can also be used to characterize photo-generated carriers 20 , 21 . The technique has a unique ability to offer high spatial resolution, as demonstrated recently with the spatial distribution of photo-generated carrier densities near individual dislocation defects 6 , 22 . However, this method is only applicable over a limited range of carrier density.…”

Section: Introductionmentioning

confidence: 99%

An all optical approach for comprehensive in-operando analysis of radiative and nonradiative recombination processes in GaAs double heterostructures

et al. 2022

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We demonstrate an all optical approach that can surprisingly offer the possibility of yielding much more information than one would expect, pertinent to the carrier recombination dynamics via both radiative and nonradiative processes when only one dominant deep defect level is present in a semiconductor material. By applying a band-defect state coupling model that explicitly treats the inter-band radiative recombination and Shockley–Read–Hall (SRH) recombination via the deep defect states on an equal footing for any defect center occupation fraction, and analyzing photoluminescence (PL) as a function of excitation density over a wide range of the excitation density (e.g., 5–6 orders in magnitude), in conjunction with Raman measurements of the LO-phonon plasmon (LOPP) coupled mode, nearly all of the key parameters relevant to the recombination processes can be obtained. They include internal quantum efficiency (IQE), minority and majority carrier density, inter-band radiative recombination rate (Wr), minority carrier nonradiative recombination rate (Wnr), defect center occupation fraction (f), defect center density (Nt), and minority and majority carrier capture cross-sections (σt and σtM). While some of this information is thought to be obtainable optically, such as IQE and the Wr/Wnr ratio, most of the other parameters are generally considered to be attainable only through electrical techniques, such as current-voltage (I-V) characteristics and deep level transient spectroscopy (DLTS). Following a procedure developed herein, this approach has been successfully applied to three GaAs double-heterostructures that exhibit two distinctly different nonradiative recombination characteristics. The method greatly enhances the usefulness of the simple PL technique to an unprecedented level, facilitating comprehensive material and device characterization without the need for any device processing.

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“…Examples include microscopy techniques such as scanning and transmission electron microscopy, for morphology, Raman spectroscopy and grazing incident angle X‐ray diffraction, for structure, time resolved photoluminescence and admittance electrical measurements, for charge carrier dynamics, X‐ray photoelectron spectroscopy, and secondary‐ion mass spectrometry, for composition, among others, where of course, final devices are the ultimate tool for performance evaluation. [ 4,11–14 ] However, the available information on the interface would benefit from an improvement in depth resolution. A local probe technique such as low‐energy muon spin spectroscopy (μSR) can study films at the nanometer scale, which will be explored in this work.…”

Section: Introductionmentioning

confidence: 99%

Characterization of the Interfacial Defect Layer in Chalcopyrite Solar Cells by Depth‐Resolved Muon Spin Spectroscopy

Alberto

Vilão

Ribeiro

et al. 2022

Adv Materials Inter

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As devices become smaller and more complex, the interfaces between adjacent materials become increasingly important and are often critical to device performance. An important research goal is to improve the interface between the absorber and the window layer by inserting buffer layers to adjust the transition. Depth‐resolved studies are key for a fundamental understanding of the interface. In the present experiment, the interface between the chalcopyrite Cu(In,Ga)Se2 absorber and various buffer layers are investigated using low‐energy muon spin rotation (μSR) spectroscopy. Depth resolution in the nm range is achieved by implanting the muons with different energies so that they stop at different depths in the sample. Near the interface, a region about 50 nm wide is detected where the lattice is more distorted than further inside the absorber. The distortion is attributed to the long‐range strain field caused by defects. These measurements allow a quantification of the corresponding passivation effect of the buffer layer. Bath‐deposited cadmium sulfide provides the best defect passivation in the near interface region, in contrast to the dry‐deposited oxides, which have a much smaller effect. The experiment demonstrates the great potential of low energy μSR spectroscopy for microscopic interfacial studies of multilayer systems.

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Impact of Individual Structural Defects in GaAs Solar Cells: A Correlative and In Operando Investigation of Signatures, Structures, and Effects

Cited by 9 publications

References 31 publications

Comprehensive,in operando, and correlative investigation of defects and their impact on device performance

Comprehensive,in operando, and correlative investigation of defects and their impact on device performance

An all optical approach for comprehensive in-operando analysis of radiative and nonradiative recombination processes in GaAs double heterostructures

Characterization of the Interfacial Defect Layer in Chalcopyrite Solar Cells by Depth‐Resolved Muon Spin Spectroscopy

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