First-principles multiple-barrier diffusion theory: The case study of interstitial diffusion in CdTe

Yang, Ji; Park, Ji-Sang; Kang, Joongoo; Wei, Su‐Huai

doi:10.1103/physrevb.91.075202

Cited by 36 publications

(30 citation statements)

References 38 publications

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“…At this step, the zone-centered phonon frequencies at the minimum sites and saddle points are calculated within the PBE 28 framework by making finite displacements (0.015 Å) and we fixed the atoms, which are more than 5 Å away from the defect centers, as we did in ref. 31 . and our results there agree well with available experimental measurements.…”

Section: Methodsmentioning

confidence: 99%

Non-Radiative Carrier Recombination Enhanced by Two-Level Process: A First-Principles Study

Yang

Shi

Wang

et al. 2016

Sci Rep

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Non-radiative recombination plays an important role in the performance of optoelectronic semiconductor devices such as solar cells and light-emitting diodes. Most textbook examples assume that the recombination process occurs through a single defect level, where one electron and one hole are captured and recombined. Based on this simple picture, conventional wisdom is that only defect levels near the center of the bandgap can be effective recombination centers. Here, we present a new two-level recombination mechanism: first, one type of carrier is captured through a defect level forming a metastable state; then the local defect configuration rapidly changes to a stable state, where the other type of carrier is captured and recombined through another defect level. This novel mechanism is applied to the recombination center in CdTe. We show that this two-level process can significantly increase the recombination rate (by three orders of magnitude) in agreement with experiments. We expect that this two-level recombination process can exist in a wide range of semiconductors, so its effect should be carefully examined in characterizing optoelectronic materials.

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Section: Methodsmentioning

confidence: 99%

Non-Radiative Carrier Recombination Enhanced by Two-Level Process: A First-Principles Study

Yang

Shi

Wang

et al. 2016

Sci Rep

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“…Using first principles parameters [24], [25], [31], fitted diffusivities, and ionization energies shown in Table I, good agreement between experiment and simulation was achieved for the annealing process with different temperatures by the same set of diffusion-reaction parameters. Solid lines in Fig.…”

Section: Simulation Results and Discussionmentioning

confidence: 61%

“…Both interstitials are active donors and they are highly mobile [24], [25]. The rate law for chemical reactions is employed to calculate the reaction rates based on the reaction constants and the concentration of the reactants…”

Section: Introductionmentioning

confidence: 99%

Numerical Simulation of Copper Migration in Single Crystal CdTe

Guo

Fang

Moore

et al. 2016

IEEE J. Photovoltaics

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Absorber material with high and stable p-type doping that does not impede free carrier lifetime is the key component enabling efficiency and stability improvements in thin-film CdTe technology. To better understand the compensation mechanism and the metastable effects related to Cu acceptors, the most common p-type dopant in CdTe, i.e., a detailed kinetic model describing the behavior of intrinsic and Cu-related defects in this material, has been developed and applied for the first time. Migration and reactions of these point defects in single crystal CdTe have been investigated by solving diffusion-reaction equations in the time-space domain self-consistently with free carrier transport. The simulation results supported by reasonable match to experimental data have shed light on the nature of limited Cu incorporation (also known as the Cu solubility limits) and Cu self-compensation during the annealing and cooling processes.

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“…This diffusion mechanism is consistent with the fast bulk P diffusion experimentally observed. Note that for a specified diffusion path, usually the largest energy barrier is dominant and will correspond to the experimental Arrhenius activation energy [37]. The GB diffusion activation energy is equivalent to the slow bulk activation energy, so it is plausible that P moving through Te sites is the primary GB diffusion mechanism.…”

Section: Resultsmentioning

confidence: 99%

Phosphorus Diffusion Mechanisms and Deep Incorporation in Polycrystalline and Single-Crystalline CdTe

Colegrove¹,

Harvey²,

Yang³

et al. 2016

Phys. Rev. Applied

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A key challenge in cadmium telluride (CdTe) semiconductors is obtaining stable and high hole density. Group I elements substituting Cd can form acceptors but easily self-compensate and diffuse quickly. For example, CdTe photovoltaics have relied on copper as a dopant, but this creates stability problems and hole density that has not exceeded 10 15 cm-3. If hole density can be increased beyond 10 16 cm-3 , CdTe solar technology can exceed multicrystalline silicon performance and provide levelized costs of electricity below conventional energy sources. Group V elements substituting Te offer a solution, but they are very difficult to incorporate. Using time-of-flight secondary-ion mass spectrometry, we examine bulk and grain boundary (GB) diffusion of phosphorous (P) in CdTe in Cd-rich conditions. We find that in addition to slow bulk diffusion and fast GB diffusion, there is a critical fast bulk diffusion component that enables deep P incorporation in CdTe. Detailed first-principles calculations indicate the slow bulk diffusion component is caused by substitutional P diffusion through the Te sublattice, whereas the fast bulk diffusion component is caused by P diffusing through interstitial lattice sites following the combination of a kick-out step and two rotation steps. The latter is limited in magnitude by high formation energy, but is sufficient to manipulate P incorporation. In addition to an increased physical understanding, this result opens up new experimental possibilities for Group V doping in CdTe applications.

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First-principles multiple-barrier diffusion theory: The case study of interstitial diffusion in CdTe

Cited by 36 publications

References 38 publications

Non-Radiative Carrier Recombination Enhanced by Two-Level Process: A First-Principles Study

Non-Radiative Carrier Recombination Enhanced by Two-Level Process: A First-Principles Study

Numerical Simulation of Copper Migration in Single Crystal CdTe

Phosphorus Diffusion Mechanisms and Deep Incorporation in Polycrystalline and Single-Crystalline CdTe

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