Characterisation of negative-<i>U</i>defects in semiconductors

Coutinho, J.; Markevich, V. P.; Peaker, А. R.

doi:10.1088/1361-648x/ab8091

Cited by 25 publications

(35 citation statements)

References 148 publications

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“…In the end the effective U = −0.46 eV. This feature is what distinguishes a negative-U defect [9], thus implying the existence of a (−/+) transition, here calculated at E c − 1.25 ± 0.02 eV.…”

Section: Vsupporting

confidence: 52%

“…These defects are termed acceptors or donors, whether they become negatively or positively charged, respectively. Consequently, trapping defects have transition energy levels, which follow directly from their charge state occupancy against the Fermi level under equilibrium conditions [9]. Traps with transition levels 0.1 eV away from the band edges can be conveniently monitored by deep-level transient spectroscopy (DLTS) or derived techniques [10].…”

Section: Introductionmentioning

confidence: 99%

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Theory of the Thermal Stability of Silicon Vacancies and Interstitials in 4H–SiC

Coutinho

2021

Crystals

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This paper presents a theoretical study of the electronic and dynamic properties of silicon vacancies and self-interstitials in 4H–SiC using hybrid density functional methods. Several pending issues, mostly related to the thermal stability of this defect, are addressed. The silicon site vacancy and the carbon-related antisite-vacancy (CAV) pair are interpreted as a unique and bistable defect. It possesses a metastable negative-U neutral state, which “disproportionates” into VSi+ or VSi−, depending on the location of the Fermi level. The vacancy introduces a (−/+) transition, calculated at Ec−1.25 eV, which determines a temperature threshold for the annealing of VSi into CAV in n-type material due to a Fermi level crossing effect. Analysis of a configuration coordinate diagram allows us to conclude that VSi anneals out in two stages—at low temperatures (T≲600 °C) via capture of a mobile species (e.g., self-interstitials) and at higher temperatures (T≳1200 °C) via dissociation into VC and CSi defects. The Si interstitial (Sii) is also a negative-U defect, with metastable q=+1 and q=+3 states. These are the only paramagnetic states of the defect, and maybe that explains why it escaped detection, even in p-type material where the migration barriers are at least 2.7 eV high.

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Section: Vsupporting

confidence: 52%

Section: Introductionmentioning

confidence: 99%

Theory of the Thermal Stability of Silicon Vacancies and Interstitials in 4H–SiC

Coutinho

2021

Crystals

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“…In recent studies by Vaqueiro‐Contreras et al [ 14 ] and Markevich et al, [ 15 ] it has been reported that the B s O 2 defect that is responsible for the hole emission signal with its maximum at 390 K in the DLTS spectra has negative‐ U properties. [ 54 ] Direct evidence of negative‐ U properties for a defect can be obtained from an analysis of temperature dependence of its occupancy ratio (occupancy function). [ 54 ] The occupancy function for a negative‐ U defect, f U <0 , differs from the Fermi function that describes the charge occupancy of defects with U > 0.…”

Section: Resultsmentioning

confidence: 99%

Indium‐Doped Silicon for Solar Cells—Light‐Induced Degradation and Deep‐Level Traps

Guzman

Markevich

Hawkins

et al. 2021

Physica Status Solidi (a)

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Indium‐doped silicon is considered a possible p‐type material for solar cells to avoid light‐induced degradation (LID), which occurs in cells made from boron‐doped Czochralski (Cz) silicon. Herein, the defect reactions associated with indium‐related LID are examined and a deep donor is detected, which is attributed to a negative‐U defect believed to be InsO2. In the presence of minority carriers or above bandgap light, the deep donor transforms to a shallow acceptor. An analogous transformation in boron‐doped material is related to the BsO2 defect that is a precursor of the center responsible for BO LID. The electronic properties of InsO2 are determined and compared to those of the BsO2 defect. Structures of the BsO2 and InsO2 defects in different charges states are found using first‐principles modeling. The results of the modeling can explain both the similarities and the differences between the BsO2 and InsO2 properties.

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“…[ 3,4 ] The negative‐U behavior (with U being the electron–electron repulsion) occurs when the ( q − 1/ q ) charge state of a defect lies closer to

E_{normalV}

than the ( q / q + 1) one. [ 34,35 ] As a consequence, only a ( q − 1/ q + 1) charge state is found in

E_{gap}

. The MP correction (Figure 1a) does not show

V_{normalN}

(+/3+) in the Kohn‐Sham

E_{gap}

.…”

Section: Validation Of the Methodologymentioning

confidence: 95%

The Electronic Properties of Chlorine in GaN: An Ab Initio Study

Fujii

Micheletto

Alfieri

2020

Physica Status Solidi (b)

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Chlorine‐based reactive ion etching (RIE) is a fundamental processing step for the manufacturing of GaN semiconductor devices. As impurities can be unintentionally incorporated in the crystal during processing, the electronic properties of chlorine in GaN are investigated. Density functional theory calculations of substitutional Cl and related complexes (with a vacancy or a dopant) are carried out. It is found that Cl and its complexes explain the reported effects of Cl RIE‐treated GaN on hole density and ohmic contact resistivity.

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Characterisation of negative-Udefects in semiconductors

Cited by 25 publications

References 148 publications

Theory of the Thermal Stability of Silicon Vacancies and Interstitials in 4H–SiC

Theory of the Thermal Stability of Silicon Vacancies and Interstitials in 4H–SiC

Indium‐Doped Silicon for Solar Cells—Light‐Induced Degradation and Deep‐Level Traps

The Electronic Properties of Chlorine in GaN: An Ab Initio Study

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